Merge branches 'torture.2014.11.03a', 'cpu.2014.11.03a', 'doc.2014.11.13a',...

Merge branches 'torture.2014.11.03a', 'cpu.2014.11.03a', 'doc.2014.11.13a', 'fixes.2014.11.13a', 'signal.2014.10.29a' and 'rt.2014.10.29a' into HEAD

cpu.2014.11.03a: Changes for per-CPU variables.
doc.2014.11.13a: Documentation updates.
fixes.2014.11.13a: Miscellaneous fixes.
signal.2014.10.29a: Signal changes.
rt.2014.10.29a: Real-time changes.
torture.2014.11.03a: torture-test changes.

Documentation/RCU/rcu.txt

@@ -36,7 +36,7 @@ o	How can the updater tell when a grace period has completed
 	executed in user mode, or executed in the idle loop, we can
 	safely free up that item.
 
-	Preemptible variants of RCU (CONFIG_TREE_PREEMPT_RCU) get the
+	Preemptible variants of RCU (CONFIG_PREEMPT_RCU) get the
 	same effect, but require that the readers manipulate CPU-local
 	counters.  These counters allow limited types of blocking within
 	RCU read-side critical sections.  SRCU also uses CPU-local
@@ -81,7 +81,7 @@ o	I hear that RCU is patented?  What is with that?
 o	I hear that RCU needs work in order to support realtime kernels?
 
 	This work is largely completed.  Realtime-friendly RCU can be
-	enabled via the CONFIG_TREE_PREEMPT_RCU kernel configuration
+	enabled via the CONFIG_PREEMPT_RCU kernel configuration
 	parameter.  However, work is in progress for enabling priority
 	boosting of preempted RCU read-side critical sections.	This is
 	needed if you have CPU-bound realtime threads.

Documentation/RCU/stallwarn.txt

@@ -26,12 +26,6 @@ CONFIG_RCU_CPU_STALL_TIMEOUT
 	Stall-warning messages may be enabled and disabled completely via
 	/sys/module/rcupdate/parameters/rcu_cpu_stall_suppress.
 
-CONFIG_RCU_CPU_STALL_VERBOSE
-
-	This kernel configuration parameter causes the stall warning to
-	also dump the stacks of any tasks that are blocking the current
-	RCU-preempt grace period.
-
 CONFIG_RCU_CPU_STALL_INFO
 
 	This kernel configuration parameter causes the stall warning to
@@ -77,7 +71,7 @@ This message indicates that CPU 5 detected that it was causing a stall,
 and that the stall was affecting RCU-sched.  This message will normally be
 followed by a stack dump of the offending CPU.  On TREE_RCU kernel builds,
 RCU and RCU-sched are implemented by the same underlying mechanism,
-while on TREE_PREEMPT_RCU kernel builds, RCU is instead implemented
+while on PREEMPT_RCU kernel builds, RCU is instead implemented
 by rcu_preempt_state.
 
 On the other hand, if the offending CPU fails to print out a stall-warning
@@ -89,7 +83,7 @@ INFO: rcu_bh_state detected stalls on CPUs/tasks: { 3 5 } (detected by 2, 2502 j
 This message indicates that CPU 2 detected that CPUs 3 and 5 were both
 causing stalls, and that the stall was affecting RCU-bh.  This message
 will normally be followed by stack dumps for each CPU.  Please note that
-TREE_PREEMPT_RCU builds can be stalled by tasks as well as by CPUs,
+PREEMPT_RCU builds can be stalled by tasks as well as by CPUs,
 and that the tasks will be indicated by PID, for example, "P3421".
 It is even possible for a rcu_preempt_state stall to be caused by both
 CPUs -and- tasks, in which case the offending CPUs and tasks will all
@@ -205,10 +199,10 @@ o	A CPU-bound real-time task in a CONFIG_PREEMPT kernel, which might
 o	A CPU-bound real-time task in a CONFIG_PREEMPT_RT kernel that
 	is running at a higher priority than the RCU softirq threads.
 	This will prevent RCU callbacks from ever being invoked,
-	and in a CONFIG_TREE_PREEMPT_RCU kernel will further prevent
+	and in a CONFIG_PREEMPT_RCU kernel will further prevent
 	RCU grace periods from ever completing.  Either way, the
 	system will eventually run out of memory and hang.  In the
-	CONFIG_TREE_PREEMPT_RCU case, you might see stall-warning
+	CONFIG_PREEMPT_RCU case, you might see stall-warning
 	messages.
 
 o	A hardware or software issue shuts off the scheduler-clock

Documentation/RCU/trace.txt

@@ -8,7 +8,7 @@ The following sections describe the debugfs files and formats, first
 for rcutree and next for rcutiny.
 
 
-CONFIG_TREE_RCU and CONFIG_TREE_PREEMPT_RCU debugfs Files and Formats
+CONFIG_TREE_RCU and CONFIG_PREEMPT_RCU debugfs Files and Formats
 
 These implementations of RCU provide several debugfs directories under the
 top-level directory "rcu":
@@ -18,7 +18,7 @@ rcu/rcu_preempt
 rcu/rcu_sched
 
 Each directory contains files for the corresponding flavor of RCU.
-Note that rcu/rcu_preempt is only present for CONFIG_TREE_PREEMPT_RCU.
+Note that rcu/rcu_preempt is only present for CONFIG_PREEMPT_RCU.
 For CONFIG_TREE_RCU, the RCU flavor maps onto the RCU-sched flavor,
 so that activity for both appears in rcu/rcu_sched.
 

Documentation/RCU/whatisRCU.txt

@@ -137,7 +137,7 @@ rcu_read_lock()
 	Used by a reader to inform the reclaimer that the reader is
 	entering an RCU read-side critical section.  It is illegal
 	to block while in an RCU read-side critical section, though
-	kernels built with CONFIG_TREE_PREEMPT_RCU can preempt RCU
+	kernels built with CONFIG_PREEMPT_RCU can preempt RCU
 	read-side critical sections.  Any RCU-protected data structure
 	accessed during an RCU read-side critical section is guaranteed to
 	remain unreclaimed for the full duration of that critical section.

Documentation/atomic_ops.txt

@@ -7,12 +7,13 @@
 maintainers on how to implement atomic counter, bitops, and spinlock
 interfaces properly.
 
-	The atomic_t type should be defined as a signed integer.
-Also, it should be made opaque such that any kind of cast to a normal
-C integer type will fail.  Something like the following should
-suffice:
+	The atomic_t type should be defined as a signed integer and
+the atomic_long_t type as a signed long integer.  Also, they should
+be made opaque such that any kind of cast to a normal C integer type
+will fail.  Something like the following should suffice:
 
 	typedef struct { int counter; } atomic_t;
+	typedef struct { long counter; } atomic_long_t;
 
 Historically, counter has been declared volatile.  This is now discouraged.
 See Documentation/volatile-considered-harmful.txt for the complete rationale.
@@ -37,6 +38,9 @@ initializer is used before runtime.  If the initializer is used at runtime, a
 proper implicit or explicit read memory barrier is needed before reading the
 value with atomic_read from another thread.
 
+As with all of the atomic_ interfaces, replace the leading "atomic_"
+with "atomic_long_" to operate on atomic_long_t.
+
 The second interface can be used at runtime, as in:
 
 	struct foo { atomic_t counter; };

Documentation/kernel-parameters.txt

@@ -2922,6 +2922,13 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			quiescent states.  Units are jiffies, minimum
 			value is one, and maximum value is HZ.
 
+	rcutree.kthread_prio= 	 [KNL,BOOT]
+			Set the SCHED_FIFO priority of the RCU
+			per-CPU kthreads (rcuc/N). This value is also
+			used for the priority of the RCU boost threads
+			(rcub/N). Valid values are 1-99 and the default
+			is 1 (the least-favored priority).
+
 	rcutree.rcu_nocb_leader_stride= [KNL]
 			Set the number of NOCB kthread groups, which
 			defaults to the square root of the number of
@@ -3071,6 +3078,15 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			messages.  Disable with a value less than or equal
 			to zero.
 
+	rcupdate.rcu_self_test= [KNL]
+			Run the RCU early boot self tests
+
+	rcupdate.rcu_self_test_bh= [KNL]
+			Run the RCU bh early boot self tests
+
+	rcupdate.rcu_self_test_sched= [KNL]
+			Run the RCU sched early boot self tests
+
 	rdinit=		[KNL]
 			Format: <full_path>
 			Run specified binary instead of /init from the ramdisk,

Documentation/memory-barriers.txt

@@ -121,22 +121,22 @@ For example, consider the following sequence of events:
 The set of accesses as seen by the memory system in the middle can be arranged
 in 24 different combinations:
 
-	STORE A=3,	STORE B=4,	x=LOAD A->3,	y=LOAD B->4
-	STORE A=3,	STORE B=4,	y=LOAD B->4,	x=LOAD A->3
-	STORE A=3,	x=LOAD A->3,	STORE B=4,	y=LOAD B->4
-	STORE A=3,	x=LOAD A->3,	y=LOAD B->2,	STORE B=4
-	STORE A=3,	y=LOAD B->2,	STORE B=4,	x=LOAD A->3
-	STORE A=3,	y=LOAD B->2,	x=LOAD A->3,	STORE B=4
-	STORE B=4,	STORE A=3,	x=LOAD A->3,	y=LOAD B->4
+	STORE A=3,	STORE B=4,	y=LOAD A->3,	x=LOAD B->4
+	STORE A=3,	STORE B=4,	x=LOAD B->4,	y=LOAD A->3
+	STORE A=3,	y=LOAD A->3,	STORE B=4,	x=LOAD B->4
+	STORE A=3,	y=LOAD A->3,	x=LOAD B->2,	STORE B=4
+	STORE A=3,	x=LOAD B->2,	STORE B=4,	y=LOAD A->3
+	STORE A=3,	x=LOAD B->2,	y=LOAD A->3,	STORE B=4
+	STORE B=4,	STORE A=3,	y=LOAD A->3,	x=LOAD B->4
 	STORE B=4, ...
 	...
 
 and can thus result in four different combinations of values:
 
-	x == 1, y == 2
-	x == 1, y == 4
-	x == 3, y == 2
-	x == 3, y == 4
+	x == 2, y == 1
+	x == 2, y == 3
+	x == 4, y == 1
+	x == 4, y == 3
 
 
 Furthermore, the stores committed by a CPU to the memory system may not be
@@ -694,6 +694,24 @@ Please note once again that the stores to 'b' differ.  If they were
 identical, as noted earlier, the compiler could pull this store outside
 of the 'if' statement.
 
+You must also be careful not to rely too much on boolean short-circuit
+evaluation.  Consider this example:
+
+	q = ACCESS_ONCE(a);
+	if (a || 1 > 0)
+		ACCESS_ONCE(b) = 1;
+
+Because the second condition is always true, the compiler can transform
+this example as following, defeating control dependency:
+
+	q = ACCESS_ONCE(a);
+	ACCESS_ONCE(b) = 1;
+
+This example underscores the need to ensure that the compiler cannot
+out-guess your code.  More generally, although ACCESS_ONCE() does force
+the compiler to actually emit code for a given load, it does not force
+the compiler to use the results.
+
 Finally, control dependencies do -not- provide transitivity.  This is
 demonstrated by two related examples, with the initial values of
 x and y both being zero:

include/linux/init_task.h

@@ -102,7 +102,7 @@ extern struct group_info init_groups;
 #define INIT_IDS
 #endif
 
-#ifdef CONFIG_TREE_PREEMPT_RCU
+#ifdef CONFIG_PREEMPT_RCU
 #define INIT_TASK_RCU_TREE_PREEMPT()					\
 	.rcu_blocked_node = NULL,
 #else

include/linux/rcupdate.h

@@ -57,7 +57,7 @@ enum rcutorture_type {
 	INVALID_RCU_FLAVOR
 };
 
-#if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU)
+#if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU)
 void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags,
 			    unsigned long *gpnum, unsigned long *completed);
 void rcutorture_record_test_transition(void);
@@ -260,7 +260,7 @@ static inline int rcu_preempt_depth(void)
 void rcu_init(void);
 void rcu_sched_qs(void);
 void rcu_bh_qs(void);
-void rcu_check_callbacks(int cpu, int user);
+void rcu_check_callbacks(int user);
 struct notifier_block;
 void rcu_idle_enter(void);
 void rcu_idle_exit(void);
@@ -348,8 +348,8 @@ extern struct srcu_struct tasks_rcu_exit_srcu;
  */
 #define cond_resched_rcu_qs() \
 do { \
-	rcu_note_voluntary_context_switch(current); \
-	cond_resched(); \
+	if (!cond_resched()) \
+		rcu_note_voluntary_context_switch(current); \
 } while (0)
 
 #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) || defined(CONFIG_SMP)
@@ -365,7 +365,7 @@ typedef void call_rcu_func_t(struct rcu_head *head,
 			     void (*func)(struct rcu_head *head));
 void wait_rcu_gp(call_rcu_func_t crf);
 
-#if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU)
+#if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU)
 #include <linux/rcutree.h>
 #elif defined(CONFIG_TINY_RCU)
 #include <linux/rcutiny.h>
@@ -852,7 +852,7 @@ static inline void rcu_preempt_sleep_check(void)
  *
  * In non-preemptible RCU implementations (TREE_RCU and TINY_RCU),
  * it is illegal to block while in an RCU read-side critical section.
- * In preemptible RCU implementations (TREE_PREEMPT_RCU) in CONFIG_PREEMPT
+ * In preemptible RCU implementations (PREEMPT_RCU) in CONFIG_PREEMPT
  * kernel builds, RCU read-side critical sections may be preempted,
  * but explicit blocking is illegal.  Finally, in preemptible RCU
  * implementations in real-time (with -rt patchset) kernel builds, RCU
@@ -887,7 +887,9 @@ static inline void rcu_read_lock(void)
  * Unfortunately, this function acquires the scheduler's runqueue and
  * priority-inheritance spinlocks.  This means that deadlock could result
  * if the caller of rcu_read_unlock() already holds one of these locks or
- * any lock that is ever acquired while holding them.
+ * any lock that is ever acquired while holding them; or any lock which
+ * can be taken from interrupt context because rcu_boost()->rt_mutex_lock()
+ * does not disable irqs while taking ->wait_lock.
  *
  * That said, RCU readers are never priority boosted unless they were
  * preempted.  Therefore, one way to avoid deadlock is to make sure
@@ -1047,6 +1049,7 @@ static inline notrace void rcu_read_unlock_sched_notrace(void)
  */
 #define RCU_INIT_POINTER(p, v) \
 	do { \
+		rcu_dereference_sparse(p, __rcu); \
 		p = RCU_INITIALIZER(v); \
 	} while (0)
 
@@ -1103,7 +1106,7 @@ static inline notrace void rcu_read_unlock_sched_notrace(void)
 	__kfree_rcu(&((ptr)->rcu_head), offsetof(typeof(*(ptr)), rcu_head))
 
 #if defined(CONFIG_TINY_RCU) || defined(CONFIG_RCU_NOCB_CPU_ALL)
-static inline int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies)
+static inline int rcu_needs_cpu(unsigned long *delta_jiffies)
 {
 	*delta_jiffies = ULONG_MAX;
 	return 0;

include/linux/rcutiny.h

@@ -78,7 +78,7 @@ static inline void kfree_call_rcu(struct rcu_head *head,
 	call_rcu(head, func);
 }
 
-static inline void rcu_note_context_switch(int cpu)
+static inline void rcu_note_context_switch(void)
 {
 	rcu_sched_qs();
 }

include/linux/rcutree.h

@@ -30,9 +30,9 @@
 #ifndef __LINUX_RCUTREE_H
 #define __LINUX_RCUTREE_H
 
-void rcu_note_context_switch(int cpu);
+void rcu_note_context_switch(void);
 #ifndef CONFIG_RCU_NOCB_CPU_ALL
-int rcu_needs_cpu(int cpu, unsigned long *delta_jiffies);
+int rcu_needs_cpu(unsigned long *delta_jiffies);
 #endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */
 void rcu_cpu_stall_reset(void);
 
@@ -43,7 +43,7 @@ void rcu_cpu_stall_reset(void);
  */
 static inline void rcu_virt_note_context_switch(int cpu)
 {
-	rcu_note_context_switch(cpu);
+	rcu_note_context_switch();
 }
 
 void synchronize_rcu_bh(void);

include/linux/sched.h

@@ -1278,9 +1278,9 @@ struct task_struct {
 	union rcu_special rcu_read_unlock_special;
 	struct list_head rcu_node_entry;
 #endif /* #ifdef CONFIG_PREEMPT_RCU */
-#ifdef CONFIG_TREE_PREEMPT_RCU
+#ifdef CONFIG_PREEMPT_RCU
 	struct rcu_node *rcu_blocked_node;
-#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
+#endif /* #ifdef CONFIG_PREEMPT_RCU */
 #ifdef CONFIG_TASKS_RCU
 	unsigned long rcu_tasks_nvcsw;
 	bool rcu_tasks_holdout;

include/trace/events/rcu.h

@@ -36,7 +36,7 @@ TRACE_EVENT(rcu_utilization,
 
 #ifdef CONFIG_RCU_TRACE
 
-#if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU)
+#if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU)
 
 /*
  * Tracepoint for grace-period events.  Takes a string identifying the
@@ -345,7 +345,7 @@ TRACE_EVENT(rcu_fqs,
 		  __entry->cpu, __entry->qsevent)
 );
 
-#endif /* #if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) */
+#endif /* #if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU) */
 
 /*
  * Tracepoint for dyntick-idle entry/exit events.  These take a string

init/Kconfig

@@ -477,7 +477,7 @@ config TREE_RCU
 	  thousands of CPUs.  It also scales down nicely to
 	  smaller systems.
 
-config TREE_PREEMPT_RCU
+config PREEMPT_RCU
 	bool "Preemptible tree-based hierarchical RCU"
 	depends on PREEMPT
 	select IRQ_WORK
@@ -501,12 +501,6 @@ config TINY_RCU
 
 endchoice
 
-config PREEMPT_RCU
-	def_bool TREE_PREEMPT_RCU
-	help
-	  This option enables preemptible-RCU code that is common between
-	  TREE_PREEMPT_RCU and, in the old days, TINY_PREEMPT_RCU.
-
 config TASKS_RCU
 	bool "Task_based RCU implementation using voluntary context switch"
 	default n
@@ -518,7 +512,7 @@ config TASKS_RCU
 	  If unsure, say N.
 
 config RCU_STALL_COMMON
-	def_bool ( TREE_RCU || TREE_PREEMPT_RCU || RCU_TRACE )
+	def_bool ( TREE_RCU || PREEMPT_RCU || RCU_TRACE )
 	help
 	  This option enables RCU CPU stall code that is common between
 	  the TINY and TREE variants of RCU.  The purpose is to allow
@@ -576,7 +570,7 @@ config RCU_FANOUT
 	int "Tree-based hierarchical RCU fanout value"
 	range 2 64 if 64BIT
 	range 2 32 if !64BIT
-	depends on TREE_RCU || TREE_PREEMPT_RCU
+	depends on TREE_RCU || PREEMPT_RCU
 	default 64 if 64BIT
 	default 32 if !64BIT
 	help
@@ -596,7 +590,7 @@ config RCU_FANOUT_LEAF
 	int "Tree-based hierarchical RCU leaf-level fanout value"
 	range 2 RCU_FANOUT if 64BIT
 	range 2 RCU_FANOUT if !64BIT
-	depends on TREE_RCU || TREE_PREEMPT_RCU
+	depends on TREE_RCU || PREEMPT_RCU
 	default 16
 	help
 	  This option controls the leaf-level fanout of hierarchical
@@ -621,7 +615,7 @@ config RCU_FANOUT_LEAF
 
 config RCU_FANOUT_EXACT
 	bool "Disable tree-based hierarchical RCU auto-balancing"
-	depends on TREE_RCU || TREE_PREEMPT_RCU
+	depends on TREE_RCU || PREEMPT_RCU
 	default n
 	help
 	  This option forces use of the exact RCU_FANOUT value specified,
@@ -652,11 +646,11 @@ config RCU_FAST_NO_HZ
 	  Say N if you are unsure.
 
 config TREE_RCU_TRACE
-	def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
+	def_bool RCU_TRACE && ( TREE_RCU || PREEMPT_RCU )
 	select DEBUG_FS
 	help
 	  This option provides tracing for the TREE_RCU and
-	  TREE_PREEMPT_RCU implementations, permitting Makefile to
+	  PREEMPT_RCU implementations, permitting Makefile to
 	  trivially select kernel/rcutree_trace.c.
 
 config RCU_BOOST
@@ -672,30 +666,31 @@ config RCU_BOOST
 	  Say Y here if you are working with real-time apps or heavy loads
 	  Say N here if you are unsure.
 
-config RCU_BOOST_PRIO
-	int "Real-time priority to boost RCU readers to"
+config RCU_KTHREAD_PRIO
+	int "Real-time priority to use for RCU worker threads"
 	range 1 99
 	depends on RCU_BOOST
 	default 1
 	help
-	  This option specifies the real-time priority to which long-term
-	  preempted RCU readers are to be boosted.  If you are working
-	  with a real-time application that has one or more CPU-bound
-	  threads running at a real-time priority level, you should set
-	  RCU_BOOST_PRIO to a priority higher then the highest-priority
-	  real-time CPU-bound thread.  The default RCU_BOOST_PRIO value
-	  of 1 is appropriate in the common case, which is real-time
+	  This option specifies the SCHED_FIFO priority value that will be
+	  assigned to the rcuc/n and rcub/n threads and is also the value
+	  used for RCU_BOOST (if enabled). If you are working with a
+	  real-time application that has one or more CPU-bound threads
+	  running at a real-time priority level, you should set
+	  RCU_KTHREAD_PRIO to a priority higher than the highest-priority
+	  real-time CPU-bound application thread.  The default RCU_KTHREAD_PRIO
+	  value of 1 is appropriate in the common case, which is real-time
 	  applications that do not have any CPU-bound threads.
 
 	  Some real-time applications might not have a single real-time
 	  thread that saturates a given CPU, but instead might have
 	  multiple real-time threads that, taken together, fully utilize
-	  that CPU.  In this case, you should set RCU_BOOST_PRIO to
+	  that CPU.  In this case, you should set RCU_KTHREAD_PRIO to
 	  a priority higher than the lowest-priority thread that is
 	  conspiring to prevent the CPU from running any non-real-time
 	  tasks.  For example, if one thread at priority 10 and another
 	  thread at priority 5 are between themselves fully consuming
-	  the CPU time on a given CPU, then RCU_BOOST_PRIO should be
+	  the CPU time on a given CPU, then RCU_KTHREAD_PRIO should be
 	  set to priority 6 or higher.
 
 	  Specify the real-time priority, or take the default if unsure.
@@ -715,7 +710,7 @@ config RCU_BOOST_DELAY
 
 config RCU_NOCB_CPU
 	bool "Offload RCU callback processing from boot-selected CPUs"
-	depends on TREE_RCU || TREE_PREEMPT_RCU
+	depends on TREE_RCU || PREEMPT_RCU
 	default n
 	help
 	  Use this option to reduce OS jitter for aggressive HPC or
@@ -739,6 +734,7 @@ config RCU_NOCB_CPU
 choice
 	prompt "Build-forced no-CBs CPUs"
 	default RCU_NOCB_CPU_NONE
+	depends on RCU_NOCB_CPU
 	help
 	  This option allows no-CBs CPUs (whose RCU callbacks are invoked
 	  from kthreads rather than from softirq context) to be specified
@@ -747,7 +743,6 @@ choice
 
 config RCU_NOCB_CPU_NONE
 	bool "No build_forced no-CBs CPUs"
-	depends on RCU_NOCB_CPU
 	help
 	  This option does not force any of the CPUs to be no-CBs CPUs.
 	  Only CPUs designated by the rcu_nocbs= boot parameter will be
@@ -761,7 +756,6 @@ config RCU_NOCB_CPU_NONE
 
 config RCU_NOCB_CPU_ZERO
 	bool "CPU 0 is a build_forced no-CBs CPU"
-	depends on RCU_NOCB_CPU
 	help
 	  This option forces CPU 0 to be a no-CBs CPU, so that its RCU
 	  callbacks are invoked by a per-CPU kthread whose name begins
@@ -776,7 +770,6 @@ config RCU_NOCB_CPU_ZERO
 
 config RCU_NOCB_CPU_ALL
 	bool "All CPUs are build_forced no-CBs CPUs"
-	depends on RCU_NOCB_CPU
 	help
 	  This option forces all CPUs to be no-CBs CPUs.  The rcu_nocbs=
 	  boot parameter will be ignored.  All CPUs' RCU callbacks will

kernel/cpu.c

@@ -86,6 +86,16 @@ static struct {
 #define cpuhp_lock_acquire()      lock_map_acquire(&cpu_hotplug.dep_map)
 #define cpuhp_lock_release()      lock_map_release(&cpu_hotplug.dep_map)
 
+static void apply_puts_pending(int max)
+{
+	int delta;
+
+	if (atomic_read(&cpu_hotplug.puts_pending) >= max) {
+		delta = atomic_xchg(&cpu_hotplug.puts_pending, 0);
+		cpu_hotplug.refcount -= delta;
+	}
+}
+
 void get_online_cpus(void)
 {
 	might_sleep();
@@ -93,6 +103,7 @@ void get_online_cpus(void)
 		return;
 	cpuhp_lock_acquire_read();
 	mutex_lock(&cpu_hotplug.lock);
+	apply_puts_pending(65536);
 	cpu_hotplug.refcount++;
 	mutex_unlock(&cpu_hotplug.lock);
 }
@@ -105,6 +116,7 @@ bool try_get_online_cpus(void)
 	if (!mutex_trylock(&cpu_hotplug.lock))
 		return false;
 	cpuhp_lock_acquire_tryread();
+	apply_puts_pending(65536);
 	cpu_hotplug.refcount++;
 	mutex_unlock(&cpu_hotplug.lock);
 	return true;
@@ -161,12 +173,7 @@ void cpu_hotplug_begin(void)
 	cpuhp_lock_acquire();
 	for (;;) {
 		mutex_lock(&cpu_hotplug.lock);
-		if (atomic_read(&cpu_hotplug.puts_pending)) {
-			int delta;
-
-			delta = atomic_xchg(&cpu_hotplug.puts_pending, 0);
-			cpu_hotplug.refcount -= delta;
-		}
+		apply_puts_pending(1);
 		if (likely(!cpu_hotplug.refcount))
 			break;
 		__set_current_state(TASK_UNINTERRUPTIBLE);

kernel/fork.c

@@ -1022,11 +1022,14 @@ void __cleanup_sighand(struct sighand_struct *sighand)
 {
 	if (atomic_dec_and_test(&sighand->count)) {
 		signalfd_cleanup(sighand);
+		/*
+		 * sighand_cachep is SLAB_DESTROY_BY_RCU so we can free it
+		 * without an RCU grace period, see __lock_task_sighand().
+		 */
 		kmem_cache_free(sighand_cachep, sighand);
 	}
 }
 
-
 /*
  * Initialize POSIX timer handling for a thread group.
  */

kernel/rcu/Makefile

 obj-y += update.o srcu.o
 obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o
 obj-$(CONFIG_TREE_RCU) += tree.o
-obj-$(CONFIG_TREE_PREEMPT_RCU) += tree.o
+obj-$(CONFIG_PREEMPT_RCU) += tree.o
 obj-$(CONFIG_TREE_RCU_TRACE) += tree_trace.o
 obj-$(CONFIG_TINY_RCU) += tiny.o

kernel/rcu/tiny.c

@@ -247,7 +247,7 @@ void rcu_bh_qs(void)
  * be called from hardirq context.  It is normally called from the
  * scheduling-clock interrupt.
  */
-void rcu_check_callbacks(int cpu, int user)
+void rcu_check_callbacks(int user)
 {
 	RCU_TRACE(check_cpu_stalls());
 	if (user || rcu_is_cpu_rrupt_from_idle())

kernel/rcu/tree.c

@@ -105,7 +105,7 @@ struct rcu_state sname##_state = { \
 	.name = RCU_STATE_NAME(sname), \
 	.abbr = sabbr, \
 }; \
-DEFINE_PER_CPU(struct rcu_data, sname##_data)
+DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_data, sname##_data)
 
 RCU_STATE_INITIALIZER(rcu_sched, 's', call_rcu_sched);
 RCU_STATE_INITIALIZER(rcu_bh, 'b', call_rcu_bh);
@@ -152,19 +152,6 @@ EXPORT_SYMBOL_GPL(rcu_scheduler_active);
  */
 static int rcu_scheduler_fully_active __read_mostly;
 
-#ifdef CONFIG_RCU_BOOST
-
-/*
- * Control variables for per-CPU and per-rcu_node kthreads.  These
- * handle all flavors of RCU.
- */
-static DEFINE_PER_CPU(struct task_struct *, rcu_cpu_kthread_task);
-DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status);
-DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_loops);
-DEFINE_PER_CPU(char, rcu_cpu_has_work);
-
-#endif /* #ifdef CONFIG_RCU_BOOST */
-
 static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu);
 static void invoke_rcu_core(void);
 static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp);
@@ -286,11 +273,11 @@ static void rcu_momentary_dyntick_idle(void)
  * and requires special handling for preemptible RCU.
  * The caller must have disabled preemption.
  */
-void rcu_note_context_switch(int cpu)
+void rcu_note_context_switch(void)
 {
 	trace_rcu_utilization(TPS("Start context switch"));
 	rcu_sched_qs();
-	rcu_preempt_note_context_switch(cpu);
+	rcu_preempt_note_context_switch();
 	if (unlikely(raw_cpu_read(rcu_sched_qs_mask)))
 		rcu_momentary_dyntick_idle();
 	trace_rcu_utilization(TPS("End context switch"));
@@ -325,7 +312,7 @@ static void force_qs_rnp(struct rcu_state *rsp,
 				  unsigned long *maxj),
 			 bool *isidle, unsigned long *maxj);
 static void force_quiescent_state(struct rcu_state *rsp);
-static int rcu_pending(int cpu);
+static int rcu_pending(void);
 
 /*
  * Return the number of RCU-sched batches processed thus far for debug & stats.
@@ -510,11 +497,11 @@ cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp)
  * we really have entered idle, and must do the appropriate accounting.
  * The caller must have disabled interrupts.
  */
-static void rcu_eqs_enter_common(struct rcu_dynticks *rdtp, long long oldval,
-				bool user)
+static void rcu_eqs_enter_common(long long oldval, bool user)
 {
 	struct rcu_state *rsp;
 	struct rcu_data *rdp;
+	struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
 
 	trace_rcu_dyntick(TPS("Start"), oldval, rdtp->dynticks_nesting);
 	if (!user && !is_idle_task(current)) {
@@ -531,7 +518,7 @@ static void rcu_eqs_enter_common(struct rcu_dynticks *rdtp, long long oldval,
 		rdp = this_cpu_ptr(rsp->rda);
 		do_nocb_deferred_wakeup(rdp);
 	}
-	rcu_prepare_for_idle(smp_processor_id());
+	rcu_prepare_for_idle();
 	/* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
 	smp_mb__before_atomic();  /* See above. */
 	atomic_inc(&rdtp->dynticks);
@@ -565,7 +552,7 @@ static void rcu_eqs_enter(bool user)
 	WARN_ON_ONCE((oldval & DYNTICK_TASK_NEST_MASK) == 0);
 	if ((oldval & DYNTICK_TASK_NEST_MASK) == DYNTICK_TASK_NEST_VALUE) {
 		rdtp->dynticks_nesting = 0;
-		rcu_eqs_enter_common(rdtp, oldval, user);
+		rcu_eqs_enter_common(oldval, user);
 	} else {
 		rdtp->dynticks_nesting -= DYNTICK_TASK_NEST_VALUE;
 	}
@@ -589,7 +576,7 @@ void rcu_idle_enter(void)
 
 	local_irq_save(flags);
 	rcu_eqs_enter(false);
-	rcu_sysidle_enter(this_cpu_ptr(&rcu_dynticks), 0);
+	rcu_sysidle_enter(0);
 	local_irq_restore(flags);
 }
 EXPORT_SYMBOL_GPL(rcu_idle_enter);
@@ -639,8 +626,8 @@ void rcu_irq_exit(void)
 	if (rdtp->dynticks_nesting)
 		trace_rcu_dyntick(TPS("--="), oldval, rdtp->dynticks_nesting);
 	else
-		rcu_eqs_enter_common(rdtp, oldval, true);
-	rcu_sysidle_enter(rdtp, 1);
+		rcu_eqs_enter_common(oldval, true);
+	rcu_sysidle_enter(1);
 	local_irq_restore(flags);
 }
 
@@ -651,16 +638,17 @@ void rcu_irq_exit(void)
  * we really have exited idle, and must do the appropriate accounting.
  * The caller must have disabled interrupts.
  */
-static void rcu_eqs_exit_common(struct rcu_dynticks *rdtp, long long oldval,
-			       int user)
+static void rcu_eqs_exit_common(long long oldval, int user)
 {
+	struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
+
 	rcu_dynticks_task_exit();
 	smp_mb__before_atomic();  /* Force ordering w/previous sojourn. */
 	atomic_inc(&rdtp->dynticks);
 	/* CPUs seeing atomic_inc() must see later RCU read-side crit sects */
 	smp_mb__after_atomic();  /* See above. */
 	WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
-	rcu_cleanup_after_idle(smp_processor_id());
+	rcu_cleanup_after_idle();
 	trace_rcu_dyntick(TPS("End"), oldval, rdtp->dynticks_nesting);
 	if (!user && !is_idle_task(current)) {
 		struct task_struct *idle __maybe_unused =
@@ -691,7 +679,7 @@ static void rcu_eqs_exit(bool user)
 		rdtp->dynticks_nesting += DYNTICK_TASK_NEST_VALUE;
 	} else {
 		rdtp->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;
-		rcu_eqs_exit_common(rdtp, oldval, user);
+		rcu_eqs_exit_common(oldval, user);
 	}
 }
 
@@ -712,7 +700,7 @@ void rcu_idle_exit(void)
 
 	local_irq_save(flags);
 	rcu_eqs_exit(false);
-	rcu_sysidle_exit(this_cpu_ptr(&rcu_dynticks), 0);
+	rcu_sysidle_exit(0);
 	local_irq_restore(flags);
 }
 EXPORT_SYMBOL_GPL(rcu_idle_exit);
@@ -763,8 +751,8 @@ void rcu_irq_enter(void)
 	if (oldval)
 		trace_rcu_dyntick(TPS("++="), oldval, rdtp->dynticks_nesting);
 	else
-		rcu_eqs_exit_common(rdtp, oldval, true);
-	rcu_sysidle_exit(rdtp, 1);
+		rcu_eqs_exit_common(oldval, true);
+	rcu_sysidle_exit(1);
 	local_irq_restore(flags);
 }
 
@@ -2387,7 +2375,7 @@ static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp)
  * invoked from the scheduling-clock interrupt.  If rcu_pending returns
  * false, there is no point in invoking rcu_check_callbacks().
  */
-void rcu_check_callbacks(int cpu, int user)
+void rcu_check_callbacks(int user)
 {
 	trace_rcu_utilization(TPS("Start scheduler-tick"));
 	increment_cpu_stall_ticks();
@@ -2419,8 +2407,8 @@ void rcu_check_callbacks(int cpu, int user)
 
 		rcu_bh_qs();
 	}
-	rcu_preempt_check_callbacks(cpu);
-	if (rcu_pending(cpu))
+	rcu_preempt_check_callbacks();
+	if (rcu_pending())
 		invoke_rcu_core();
 	if (user)
 		rcu_note_voluntary_context_switch(current);
@@ -2963,6 +2951,9 @@ static int synchronize_sched_expedited_cpu_stop(void *data)
  */
 void synchronize_sched_expedited(void)
 {
+	cpumask_var_t cm;
+	bool cma = false;
+	int cpu;
 	long firstsnap, s, snap;
 	int trycount = 0;
 	struct rcu_state *rsp = &rcu_sched_state;
@@ -2997,11 +2988,26 @@ void synchronize_sched_expedited(void)
 	}
 	WARN_ON_ONCE(cpu_is_offline(raw_smp_processor_id()));
 
+	/* Offline CPUs, idle CPUs, and any CPU we run on are quiescent. */
+	cma = zalloc_cpumask_var(&cm, GFP_KERNEL);
+	if (cma) {
+		cpumask_copy(cm, cpu_online_mask);
+		cpumask_clear_cpu(raw_smp_processor_id(), cm);
+		for_each_cpu(cpu, cm) {
+			struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
+
+			if (!(atomic_add_return(0, &rdtp->dynticks) & 0x1))
+				cpumask_clear_cpu(cpu, cm);
+		}
+		if (cpumask_weight(cm) == 0)
+			goto all_cpus_idle;
+	}
+
 	/*
 	 * Each pass through the following loop attempts to force a
 	 * context switch on each CPU.
 	 */
-	while (try_stop_cpus(cpu_online_mask,
+	while (try_stop_cpus(cma ? cm : cpu_online_mask,
 			     synchronize_sched_expedited_cpu_stop,
 			     NULL) == -EAGAIN) {
 		put_online_cpus();
@@ -3013,6 +3019,7 @@ void synchronize_sched_expedited(void)
 			/* ensure test happens before caller kfree */
 			smp_mb__before_atomic(); /* ^^^ */
 			atomic_long_inc(&rsp->expedited_workdone1);
+			free_cpumask_var(cm);
 			return;
 		}
 
@@ -3022,6 +3029,7 @@ void synchronize_sched_expedited(void)
 		} else {
 			wait_rcu_gp(call_rcu_sched);
 			atomic_long_inc(&rsp->expedited_normal);
+			free_cpumask_var(cm);
 			return;
 		}
 
@@ -3031,6 +3039,7 @@ void synchronize_sched_expedited(void)
 			/* ensure test happens before caller kfree */
 			smp_mb__before_atomic(); /* ^^^ */
 			atomic_long_inc(&rsp->expedited_workdone2);
+			free_cpumask_var(cm);
 			return;
 		}
 
@@ -3045,6 +3054,7 @@ void synchronize_sched_expedited(void)
 			/* CPU hotplug operation in flight, use normal GP. */
 			wait_rcu_gp(call_rcu_sched);
 			atomic_long_inc(&rsp->expedited_normal);
+			free_cpumask_var(cm);
 			return;
 		}
 		snap = atomic_long_read(&rsp->expedited_start);
@@ -3052,6 +3062,9 @@ void synchronize_sched_expedited(void)
 	}
 	atomic_long_inc(&rsp->expedited_stoppedcpus);
 
+all_cpus_idle:
+	free_cpumask_var(cm);
+
 	/*
 	 * Everyone up to our most recent fetch is covered by our grace
 	 * period.  Update the counter, but only if our work is still
@@ -3143,12 +3156,12 @@ static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp)
  * by the current CPU, returning 1 if so.  This function is part of the
  * RCU implementation; it is -not- an exported member of the RCU API.
  */
-static int rcu_pending(int cpu)
+static int rcu_pending(void)
 {
 	struct rcu_state *rsp;
 
 	for_each_rcu_flavor(rsp)
-		if (__rcu_pending(rsp, per_cpu_ptr(rsp->rda, cpu)))
+		if (__rcu_pending(rsp, this_cpu_ptr(rsp->rda)))
 			return 1;
 	return 0;
 }
@@ -3158,7 +3171,7 @@ static int rcu_pending(int cpu)
  * non-NULL, store an indication of whether all callbacks are lazy.
  * (If there are no callbacks, all of them are deemed to be lazy.)
  */
-static int __maybe_unused rcu_cpu_has_callbacks(int cpu, bool *all_lazy)
+static int __maybe_unused rcu_cpu_has_callbacks(bool *all_lazy)
 {
 	bool al = true;
 	bool hc = false;
@@ -3166,7 +3179,7 @@ static int __maybe_unused rcu_cpu_has_callbacks(int cpu, bool *all_lazy)
 	struct rcu_state *rsp;
 
 	for_each_rcu_flavor(rsp) {
-		rdp = per_cpu_ptr(rsp->rda, cpu);
+		rdp = this_cpu_ptr(rsp->rda);
 		if (!rdp->nxtlist)
 			continue;
 		hc = true;
@@ -3485,8 +3498,10 @@ static int rcu_cpu_notify(struct notifier_block *self,
 	case CPU_DEAD_FROZEN:
 	case CPU_UP_CANCELED:
 	case CPU_UP_CANCELED_FROZEN:
-		for_each_rcu_flavor(rsp)
+		for_each_rcu_flavor(rsp) {
 			rcu_cleanup_dead_cpu(cpu, rsp);
+			do_nocb_deferred_wakeup(per_cpu_ptr(rsp->rda, cpu));
+		}
 		break;
 	default:
 		break;

kernel/rcu/tree.h

@@ -139,7 +139,7 @@ struct rcu_node {
 	unsigned long expmask;	/* Groups that have ->blkd_tasks */
 				/*  elements that need to drain to allow the */
 				/*  current expedited grace period to */
-				/*  complete (only for TREE_PREEMPT_RCU). */
+				/*  complete (only for PREEMPT_RCU). */
 	unsigned long qsmaskinit;
 				/* Per-GP initial value for qsmask & expmask. */
 	unsigned long grpmask;	/* Mask to apply to parent qsmask. */
@@ -530,10 +530,10 @@ DECLARE_PER_CPU(struct rcu_data, rcu_sched_data);
 extern struct rcu_state rcu_bh_state;
 DECLARE_PER_CPU(struct rcu_data, rcu_bh_data);
 
-#ifdef CONFIG_TREE_PREEMPT_RCU
+#ifdef CONFIG_PREEMPT_RCU
 extern struct rcu_state rcu_preempt_state;
 DECLARE_PER_CPU(struct rcu_data, rcu_preempt_data);
-#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
+#endif /* #ifdef CONFIG_PREEMPT_RCU */
 
 #ifdef CONFIG_RCU_BOOST
 DECLARE_PER_CPU(unsigned int, rcu_cpu_kthread_status);
@@ -547,7 +547,7 @@ DECLARE_PER_CPU(char, rcu_cpu_has_work);
 /* Forward declarations for rcutree_plugin.h */
 static void rcu_bootup_announce(void);
 long rcu_batches_completed(void);
-static void rcu_preempt_note_context_switch(int cpu);
+static void rcu_preempt_note_context_switch(void);
 static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp);
 #ifdef CONFIG_HOTPLUG_CPU
 static void rcu_report_unblock_qs_rnp(struct rcu_node *rnp,
@@ -561,12 +561,12 @@ static int rcu_preempt_offline_tasks(struct rcu_state *rsp,
 				     struct rcu_node *rnp,
 				     struct rcu_data *rdp);
 #endif /* #ifdef CONFIG_HOTPLUG_CPU */
-static void rcu_preempt_check_callbacks(int cpu);
+static void rcu_preempt_check_callbacks(void);
 void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu));
-#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_TREE_PREEMPT_RCU)
+#if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_PREEMPT_RCU)
 static void rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
 			       bool wake);
-#endif /* #if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_TREE_PREEMPT_RCU) */
+#endif /* #if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_PREEMPT_RCU) */
 static void __init __rcu_init_preempt(void);
 static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags);
 static void rcu_preempt_boost_start_gp(struct rcu_node *rnp);
@@ -579,8 +579,8 @@ static int rcu_spawn_one_boost_kthread(struct rcu_state *rsp,
 #endif /* #ifdef CONFIG_RCU_BOOST */
 static void __init rcu_spawn_boost_kthreads(void);
 static void rcu_prepare_kthreads(int cpu);
-static void rcu_cleanup_after_idle(int cpu);
-static void rcu_prepare_for_idle(int cpu);
+static void rcu_cleanup_after_idle(void);
+static void rcu_prepare_for_idle(void);
 static void rcu_idle_count_callbacks_posted(void);
 static void print_cpu_stall_info_begin(void);
 static void print_cpu_stall_info(struct rcu_state *rsp, int cpu);
@@ -606,8 +606,8 @@ static void __init rcu_organize_nocb_kthreads(struct rcu_state *rsp);
 #endif /* #ifdef CONFIG_RCU_NOCB_CPU */
 static void __maybe_unused rcu_kick_nohz_cpu(int cpu);
 static bool init_nocb_callback_list(struct rcu_data *rdp);
-static void rcu_sysidle_enter(struct rcu_dynticks *rdtp, int irq);
-static void rcu_sysidle_exit(struct rcu_dynticks *rdtp, int irq);
+static void rcu_sysidle_enter(int irq);
+static void rcu_sysidle_exit(int irq);
 static void rcu_sysidle_check_cpu(struct rcu_data *rdp, bool *isidle,
 				  unsigned long *maxj);
 static bool is_sysidle_rcu_state(struct rcu_state *rsp);

kernel/rcu/update.c

@@ -306,7 +306,7 @@ struct debug_obj_descr rcuhead_debug_descr = {
 EXPORT_SYMBOL_GPL(rcuhead_debug_descr);
 #endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
 
-#if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) || defined(CONFIG_RCU_TRACE)
+#if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU) || defined(CONFIG_RCU_TRACE)
 void do_trace_rcu_torture_read(const char *rcutorturename, struct rcu_head *rhp,
 			       unsigned long secs,
 			       unsigned long c_old, unsigned long c)
@@ -531,7 +531,8 @@ static int __noreturn rcu_tasks_kthread(void *arg)
 	struct rcu_head *next;
 	LIST_HEAD(rcu_tasks_holdouts);
 
-	/* FIXME: Add housekeeping affinity. */
+	/* Run on housekeeping CPUs by default.  Sysadm can move if desired. */
+	housekeeping_affine(current);
 
 	/*
 	 * Each pass through the following loop makes one check for

kernel/sched/core.c

@@ -2802,7 +2802,7 @@ static void __sched __schedule(void)
 	preempt_disable();
 	cpu = smp_processor_id();
 	rq = cpu_rq(cpu);
-	rcu_note_context_switch(cpu);
+	rcu_note_context_switch();
 	prev = rq->curr;
 
 	schedule_debug(prev);

kernel/signal.c

@@ -1275,7 +1275,17 @@ struct sighand_struct *__lock_task_sighand(struct task_struct *tsk,
 			local_irq_restore(*flags);
 			break;
 		}
-
+		/*
+		 * This sighand can be already freed and even reused, but
+		 * we rely on SLAB_DESTROY_BY_RCU and sighand_ctor() which
+		 * initializes ->siglock: this slab can't go away, it has
+		 * the same object type, ->siglock can't be reinitialized.
+		 *
+		 * We need to ensure that tsk->sighand is still the same
+		 * after we take the lock, we can race with de_thread() or
+		 * __exit_signal(). In the latter case the next iteration
+		 * must see ->sighand == NULL.
+		 */
 		spin_lock(&sighand->siglock);
 		if (likely(sighand == tsk->sighand)) {
 			rcu_read_unlock();
@@ -1331,23 +1341,21 @@ int kill_pid_info(int sig, struct siginfo *info, struct pid *pid)
 	int error = -ESRCH;
 	struct task_struct *p;
 
-	rcu_read_lock();
-retry:
-	p = pid_task(pid, PIDTYPE_PID);
-	if (p) {
-		error = group_send_sig_info(sig, info, p);
-		if (unlikely(error == -ESRCH))
-			/*
-			 * The task was unhashed in between, try again.
-			 * If it is dead, pid_task() will return NULL,
-			 * if we race with de_thread() it will find the
-			 * new leader.
-			 */
-			goto retry;
-	}
-	rcu_read_unlock();
+	for (;;) {
+		rcu_read_lock();
+		p = pid_task(pid, PIDTYPE_PID);
+		if (p)
+			error = group_send_sig_info(sig, info, p);
+		rcu_read_unlock();
+		if (likely(!p || error != -ESRCH))
+			return error;
 
-	return error;
+		/*
+		 * The task was unhashed in between, try again.  If it
+		 * is dead, pid_task() will return NULL, if we race with
+		 * de_thread() it will find the new leader.
+		 */
+	}
 }
 
 int kill_proc_info(int sig, struct siginfo *info, pid_t pid)

kernel/softirq.c

@@ -656,7 +656,7 @@ static void run_ksoftirqd(unsigned int cpu)
 		 * in the task stack here.
 		 */
 		__do_softirq();
-		rcu_note_context_switch(cpu);
+		rcu_note_context_switch();
 		local_irq_enable();
 		cond_resched();
 		return;

kernel/time/tick-sched.c

@@ -585,7 +585,7 @@ static ktime_t tick_nohz_stop_sched_tick(struct tick_sched *ts,
 		last_jiffies = jiffies;
 	} while (read_seqretry(&jiffies_lock, seq));
 
-	if (rcu_needs_cpu(cpu, &rcu_delta_jiffies) ||
+	if (rcu_needs_cpu(&rcu_delta_jiffies) ||
 	    arch_needs_cpu() || irq_work_needs_cpu()) {
 		next_jiffies = last_jiffies + 1;
 		delta_jiffies = 1;

kernel/time/timer.c

@@ -1377,12 +1377,11 @@ unsigned long get_next_timer_interrupt(unsigned long now)
 void update_process_times(int user_tick)
 {
 	struct task_struct *p = current;
-	int cpu = smp_processor_id();
 
 	/* Note: this timer irq context must be accounted for as well. */
 	account_process_tick(p, user_tick);
 	run_local_timers();
-	rcu_check_callbacks(cpu, user_tick);
+	rcu_check_callbacks(user_tick);
 #ifdef CONFIG_IRQ_WORK
 	if (in_irq())
 		irq_work_tick();

lib/Kconfig.debug

@@ -1238,21 +1238,9 @@ config RCU_CPU_STALL_TIMEOUT
 	  RCU grace period persists, additional CPU stall warnings are
 	  printed at more widely spaced intervals.
 
-config RCU_CPU_STALL_VERBOSE
-	bool "Print additional per-task information for RCU_CPU_STALL_DETECTOR"
-	depends on TREE_PREEMPT_RCU
-	default y
-	help
-	  This option causes RCU to printk detailed per-task information
-	  for any tasks that are stalling the current RCU grace period.
-
-	  Say N if you are unsure.
-
-	  Say Y if you want to enable such checks.
-
 config RCU_CPU_STALL_INFO
 	bool "Print additional diagnostics on RCU CPU stall"
-	depends on (TREE_RCU || TREE_PREEMPT_RCU) && DEBUG_KERNEL
+	depends on (TREE_RCU || PREEMPT_RCU) && DEBUG_KERNEL
 	default n
 	help
 	  For each stalled CPU that is aware of the current RCU grace

tools/testing/selftests/rcutorture/configs/rcu/TREE01

@@ -2,7 +2,7 @@ CONFIG_SMP=y
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-#CHECK#CONFIG_TREE_PREEMPT_RCU=y
+#CHECK#CONFIG_PREEMPT_RCU=y
 CONFIG_HZ_PERIODIC=n
 CONFIG_NO_HZ_IDLE=y
 CONFIG_NO_HZ_FULL=n
@@ -14,6 +14,5 @@ CONFIG_RCU_NOCB_CPU=y
 CONFIG_RCU_NOCB_CPU_ZERO=y
 CONFIG_DEBUG_LOCK_ALLOC=n
 CONFIG_RCU_CPU_STALL_INFO=n
-CONFIG_RCU_CPU_STALL_VERBOSE=n
 CONFIG_RCU_BOOST=n
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=n

tools/testing/selftests/rcutorture/configs/rcu/TREE02

@@ -3,7 +3,7 @@ CONFIG_NR_CPUS=8
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-#CHECK#CONFIG_TREE_PREEMPT_RCU=y
+#CHECK#CONFIG_PREEMPT_RCU=y
 CONFIG_HZ_PERIODIC=n
 CONFIG_NO_HZ_IDLE=y
 CONFIG_NO_HZ_FULL=n
@@ -19,6 +19,5 @@ CONFIG_RCU_NOCB_CPU=n
 CONFIG_DEBUG_LOCK_ALLOC=y
 CONFIG_PROVE_LOCKING=n
 CONFIG_RCU_CPU_STALL_INFO=n
-CONFIG_RCU_CPU_STALL_VERBOSE=y
 CONFIG_RCU_BOOST=n
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=n

tools/testing/selftests/rcutorture/configs/rcu/TREE02-T

@@ -3,7 +3,7 @@ CONFIG_NR_CPUS=8
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-#CHECK#CONFIG_TREE_PREEMPT_RCU=y
+#CHECK#CONFIG_PREEMPT_RCU=y
 CONFIG_HZ_PERIODIC=n
 CONFIG_NO_HZ_IDLE=y
 CONFIG_NO_HZ_FULL=n
@@ -19,6 +19,5 @@ CONFIG_RCU_NOCB_CPU=n
 CONFIG_DEBUG_LOCK_ALLOC=y
 CONFIG_PROVE_LOCKING=n
 CONFIG_RCU_CPU_STALL_INFO=n
-CONFIG_RCU_CPU_STALL_VERBOSE=y
 CONFIG_RCU_BOOST=n
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=n

tools/testing/selftests/rcutorture/configs/rcu/TREE03

@@ -3,7 +3,7 @@ CONFIG_NR_CPUS=8
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-#CHECK#CONFIG_TREE_PREEMPT_RCU=y
+#CHECK#CONFIG_PREEMPT_RCU=y
 CONFIG_HZ_PERIODIC=y
 CONFIG_NO_HZ_IDLE=n
 CONFIG_NO_HZ_FULL=n
@@ -15,7 +15,6 @@ CONFIG_RCU_FANOUT_EXACT=n
 CONFIG_RCU_NOCB_CPU=n
 CONFIG_DEBUG_LOCK_ALLOC=n
 CONFIG_RCU_CPU_STALL_INFO=n
-CONFIG_RCU_CPU_STALL_VERBOSE=n
 CONFIG_RCU_BOOST=y
-CONFIG_RCU_BOOST_PRIO=2
+CONFIG_RCU_KTHREAD_PRIO=2
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=n

tools/testing/selftests/rcutorture/configs/rcu/TREE04

@@ -19,5 +19,4 @@ CONFIG_RCU_FANOUT_EXACT=n
 CONFIG_RCU_NOCB_CPU=n
 CONFIG_DEBUG_LOCK_ALLOC=n
 CONFIG_RCU_CPU_STALL_INFO=y
-CONFIG_RCU_CPU_STALL_VERBOSE=y
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=n

tools/testing/selftests/rcutorture/configs/rcu/TREE05

@@ -19,5 +19,4 @@ CONFIG_DEBUG_LOCK_ALLOC=y
 CONFIG_PROVE_LOCKING=y
 CONFIG_PROVE_RCU=y
 CONFIG_RCU_CPU_STALL_INFO=n
-CONFIG_RCU_CPU_STALL_VERBOSE=n
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=n

tools/testing/selftests/rcutorture/configs/rcu/TREE06

@@ -20,5 +20,4 @@ CONFIG_DEBUG_LOCK_ALLOC=y
 CONFIG_PROVE_LOCKING=y
 CONFIG_PROVE_RCU=y
 CONFIG_RCU_CPU_STALL_INFO=n
-CONFIG_RCU_CPU_STALL_VERBOSE=n
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=y

tools/testing/selftests/rcutorture/configs/rcu/TREE07

@@ -19,5 +19,4 @@ CONFIG_RCU_FANOUT_EXACT=n
 CONFIG_RCU_NOCB_CPU=n
 CONFIG_DEBUG_LOCK_ALLOC=n
 CONFIG_RCU_CPU_STALL_INFO=y
-CONFIG_RCU_CPU_STALL_VERBOSE=n
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=n

tools/testing/selftests/rcutorture/configs/rcu/TREE08

@@ -3,7 +3,7 @@ CONFIG_NR_CPUS=16
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-#CHECK#CONFIG_TREE_PREEMPT_RCU=y
+#CHECK#CONFIG_PREEMPT_RCU=y
 CONFIG_HZ_PERIODIC=n
 CONFIG_NO_HZ_IDLE=y
 CONFIG_NO_HZ_FULL=n
@@ -21,6 +21,5 @@ CONFIG_DEBUG_LOCK_ALLOC=n
 CONFIG_PROVE_LOCKING=y
 CONFIG_PROVE_RCU=y
 CONFIG_RCU_CPU_STALL_INFO=n
-CONFIG_RCU_CPU_STALL_VERBOSE=n
 CONFIG_RCU_BOOST=n
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=n

tools/testing/selftests/rcutorture/configs/rcu/TREE08-T

@@ -3,7 +3,7 @@ CONFIG_NR_CPUS=16
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-#CHECK#CONFIG_TREE_PREEMPT_RCU=y
+#CHECK#CONFIG_PREEMPT_RCU=y
 CONFIG_HZ_PERIODIC=n
 CONFIG_NO_HZ_IDLE=y
 CONFIG_NO_HZ_FULL=n
@@ -19,6 +19,5 @@ CONFIG_RCU_NOCB_CPU=y
 CONFIG_RCU_NOCB_CPU_ALL=y
 CONFIG_DEBUG_LOCK_ALLOC=n
 CONFIG_RCU_CPU_STALL_INFO=n
-CONFIG_RCU_CPU_STALL_VERBOSE=n
 CONFIG_RCU_BOOST=n
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=n

tools/testing/selftests/rcutorture/configs/rcu/TREE09

@@ -3,7 +3,7 @@ CONFIG_NR_CPUS=1
 CONFIG_PREEMPT_NONE=n
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=y
-#CHECK#CONFIG_TREE_PREEMPT_RCU=y
+#CHECK#CONFIG_PREEMPT_RCU=y
 CONFIG_HZ_PERIODIC=n
 CONFIG_NO_HZ_IDLE=y
 CONFIG_NO_HZ_FULL=n
@@ -14,6 +14,5 @@ CONFIG_HIBERNATION=n
 CONFIG_RCU_NOCB_CPU=n
 CONFIG_DEBUG_LOCK_ALLOC=n
 CONFIG_RCU_CPU_STALL_INFO=n
-CONFIG_RCU_CPU_STALL_VERBOSE=n
 CONFIG_RCU_BOOST=n
 CONFIG_DEBUG_OBJECTS_RCU_HEAD=n

tools/testing/selftests/rcutorture/doc/TINY_RCU.txt

@@ -34,7 +34,7 @@ CONFIG_PREEMPT
 CONFIG_PREEMPT_RCU
 CONFIG_SMP
 CONFIG_TINY_RCU
-CONFIG_TREE_PREEMPT_RCU
+CONFIG_PREEMPT_RCU
 CONFIG_TREE_RCU
 
 	All forced by CONFIG_TINY_RCU.

tools/testing/selftests/rcutorture/doc/TREE_RCU-kconfig.txt

 This document gives a brief rationale for the TREE_RCU-related test
-cases, a group that includes TREE_PREEMPT_RCU.
+cases, a group that includes PREEMPT_RCU.
 
 
 Kconfig Parameters:
@@ -14,10 +14,9 @@ CONFIG_NO_HZ_FULL_SYSIDLE -- Do one.
 CONFIG_PREEMPT -- Do half.  (First three and #8.)
 CONFIG_PROVE_LOCKING -- Do all but two, covering CONFIG_PROVE_RCU and not.
 CONFIG_PROVE_RCU -- Do all but one under CONFIG_PROVE_LOCKING.
-CONFIG_RCU_BOOST -- one of TREE_PREEMPT_RCU.
-CONFIG_RCU_BOOST_PRIO -- set to 2 for _BOOST testing.
-CONFIG_RCU_CPU_STALL_INFO -- do one with and without _VERBOSE.
-CONFIG_RCU_CPU_STALL_VERBOSE -- do one with and without _INFO.
+CONFIG_RCU_BOOST -- one of PREEMPT_RCU.
+CONFIG_RCU_KTHREAD_PRIO -- set to 2 for _BOOST testing.
+CONFIG_RCU_CPU_STALL_INFO -- Do one.
 CONFIG_RCU_FANOUT -- Cover hierarchy as currently, but overlap with others.
 CONFIG_RCU_FANOUT_EXACT -- Do one.
 CONFIG_RCU_FANOUT_LEAF -- Do one non-default.
@@ -27,7 +26,7 @@ CONFIG_RCU_NOCB_CPU_ALL -- Do one.
 CONFIG_RCU_NOCB_CPU_NONE -- Do one.
 CONFIG_RCU_NOCB_CPU_ZERO -- Do one.
 CONFIG_RCU_TRACE -- Do half.
-CONFIG_SMP -- Need one !SMP for TREE_PREEMPT_RCU.
+CONFIG_SMP -- Need one !SMP for PREEMPT_RCU.
 RCU-bh: Do one with PREEMPT and one with !PREEMPT.
 RCU-sched: Do one with PREEMPT but not BOOST.
 
@@ -77,7 +76,7 @@ CONFIG_RCU_CPU_STALL_TIMEOUT
 
 CONFIG_RCU_STALL_COMMON
 
-	Implied by TREE_RCU and TREE_PREEMPT_RCU.
+	Implied by TREE_RCU and PREEMPT_RCU.
 
 CONFIG_RCU_TORTURE_TEST
 CONFIG_RCU_TORTURE_TEST_RUNNABLE
@@ -88,7 +87,7 @@ CONFIG_RCU_USER_QS
 
 	Redundant with CONFIG_NO_HZ_FULL.
 
-CONFIG_TREE_PREEMPT_RCU
+CONFIG_PREEMPT_RCU
 CONFIG_TREE_RCU
 
 	These are controlled by CONFIG_PREEMPT.