- 21 Aug, 2010 1 commit
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Arnd Bergmann authored
Also add rcu_dereference_protected() for code paths where locks are held. Signed-off-by:
Arnd Bergmann <arnd@arndb.de> Signed-off-by:
Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: "Michael S. Tsirkin" <mst@redhat.com>
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- 20 Aug, 2010 38 commits
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Paul E. McKenney authored
Because list_empty() does not dereference any RCU-protected pointers, and further does not pass such pointers to the caller (so that the caller does not dereference them either), it is safe to use list_empty() on RCU-protected lists. There is no need for a list_empty_rcu(). This commit adds a comment stating this explicitly. Requested-by:
Andrew Morton <akpm@linux-foundation.org> Signed-off-by:
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Paul E. McKenney authored
Replace one of the ACCESS_ONCE() calls in each of __rcu_read_lock() and __rcu_read_unlock() with barrier() as suggested by Steve Rostedt in order to avoid the potential compiler-optimization-induced bug noted by Mathieu Desnoyers. Located-by:
Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> Suggested-by:
Steven Rostedt <rostedt@goodmis.org> Signed-off-by:
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Paul E. McKenney authored
The CONFIG_PREEMPT_RCU kernel configuration parameter was recently re-introduced, but as an indication of the type of RCU (preemptible vs. non-preemptible) instead of as selecting a given implementation. This commit uses CONFIG_PREEMPT_RCU to combine duplicate code from include/linux/rcutiny.h and include/linux/rcutree.h into include/linux/rcupdate.h. This commit also combines a few other pieces of duplicate code that have accumulated. Signed-off-by: -
Paul E. McKenney authored
It is illegal to wait for an SRCU grace period while within the corresponding flavor of SRCU read-side critical section. Therefore, this commit updates the srcu_read_lock() docbook accordingly. Signed-off-by: -
Paul E. McKenney authored
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Paul E. McKenney authored
Combine the duplicate definitions of ULONG_CMP_GE(), ULONG_CMP_LT(), and rcu_preempt_depth() into include/linux/rcupdate.h. Signed-off-by: -
Paul E. McKenney authored
When using a kernel debugger, a long sojourn in the debugger can get you lots of RCU CPU stall warnings once you resume. This might not be helpful, especially if you are using the system console. This patch therefore allows RCU CPU stall warnings to be suppressed, but only for the duration of the current set of grace periods. This differs from Jason's original patch in that it adds support for tiny RCU and preemptible RCU, and uses a slightly different method for suppressing the RCU CPU stall warning messages. Signed-off-by:
Jason Wessel <jason.wessel@windriver.com> Signed-off-by:
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Paul E. McKenney authored
There is some documentation on RCU CPU stall warnings contained in Documentation/RCU/stallwarn.txt, but it will not be apparent to someone who runs into such a warning while under time pressure. This commit therefore adds comments preceding the printk()s pointing out the location of this documentation. Signed-off-by: -
Paul E. McKenney authored
The comment says that blocking is illegal in rcu_read_lock()-style RCU read-side critical sections, which is no longer entirely true given preemptible RCU. This commit provides a fix. Suggested-by:
David Miller <davem@davemloft.net> Signed-off-by:
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Paul E. McKenney authored
Implement a small-memory-footprint uniprocessor-only implementation of preemptible RCU. This implementation uses but a single blocked-tasks list rather than the combinatorial number used per leaf rcu_node by TREE_PREEMPT_RCU, which reduces memory consumption and greatly simplifies processing. This version also takes advantage of uniprocessor execution to accelerate grace periods in the case where there are no readers. The general design is otherwise broadly similar to that of TREE_PREEMPT_RCU. This implementation is a step towards having RCU implementation driven off of the SMP and PREEMPT kernel configuration variables, which can happen once this implementation has accumulated sufficient experience. Removed ACCESS_ONCE() from __rcu_read_unlock() and added barrier() as suggested by Steve Rostedt in order to avoid the compiler-reordering issue noted by Mathieu Desnoyers (http://lkml.org/lkml/2010/8/16/183). As can be seen below, CONFIG_TINY_PREEMPT_RCU represents almost 5Kbyte savings compared to CONFIG_TREE_PREEMPT_RCU. Of course, for non-real-time workloads, CONFIG_TINY_RCU is even better. CONFIG_TREE_PREEMPT_RCU text data bss dec filename 13 0 0 13 kernel/rcupdate.o 6170 825 28 7023 kernel/rcutree.o ---- 7026 Total CONFIG_TINY_PREEMPT_RCU text data bss dec filename 13 0 0 13 kernel/rcupdate.o 2081 81 8 2170 kernel/rcutiny.o ---- 2183 Total CONFIG_TINY_RCU (non-preemptible) text data bss dec filename 13 0 0 13 kernel/rcupdate.o 719 25 0 744 kernel/rcutiny.o --- 757 Total Requested-by:
Loïc Minier <loic.minier@canonical.com> Signed-off-by:
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Paul E. McKenney authored
Commit cf244dc0 added a fourth level to the TREE_RCU hierarchy, but the RCU_FANOUT help message still said "cube root". This commit fixes this to "fourth root" and also emphasizes that production systems are well-served by the default. (Stress-testing RCU itself uses small RCU_FANOUT values in order to test large-system code paths on small(er) systems.) Located-by:
John Kacur <jkacur@redhat.com> Signed-off-by:
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Paul E. McKenney authored
Currently, if RCU CPU stall warnings are enabled, they are enabled immediately upon boot. They can be manually disabled via /sys (and also re-enabled via /sys), and are automatically disabled upon panic. However, some users need RCU CPU stalls to be disabled at boot time, but to be enabled without rebuilding/rebooting. For example, someone running a real-time application in production might not want the additional latency of RCU CPU stall detection in normal operation, but might need to enable it at any point for fault isolation purposes. This commit therefore provides a new CONFIG_RCU_CPU_STALL_DETECTOR_RUNNABLE kernel configuration parameter that maintains the current behavior (enable at boot) by default, but allows a kernel to be configured with RCU CPU stall detection built into the kernel, but disabled at boot time. Requested-by:
Clark Williams <williams@redhat.com> Requested-by:
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Paul E. McKenney authored
Because both TINY_RCU and TREE_PREEMPT_RCU have been in mainline for several releases, it is time to restrict the use of TREE_RCU to SMP non-preemptible systems. This reduces testing/validation effort. This commit is a first step towards driving the selection of RCU implementation directly off of the SMP and PREEMPT configuration parameters. Signed-off-by: -
Paul E. McKenney authored
Set the permissions of the rcu_cpu_stall_suppress to 644 to enable RCU CPU stall warnings to be enabled and disabled at runtime via sysfs. Suggested-by:
Josh Triplett <josh@joshtriplett.org> Signed-off-by:
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Paul E. McKenney authored
Reported-by:
Kyle Hubert <khubert@gmail.com> Signed-off-by:
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Paul E. McKenney authored
Signed-off-by:
Alexey Dobriyan <adobriyan@gmail.com> Signed-off-by:
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Mathieu Desnoyers authored
RCU heads really don't need to be initialized. Their state before call_rcu() really does not matter. We need to keep init/destroy_rcu_head_on_stack() though, since we want debugobjects to be able to keep track of these objects. Signed-off-by:
Mathieu Desnoyers <mathieu.desnoyers@efficios.com> CC: David S. Miller <davem@davemloft.net> CC: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> CC: akpm@linux-foundation.org CC: mingo@elte.hu CC: laijs@cn.fujitsu.com CC: dipankar@in.ibm.com CC: josh@joshtriplett.org CC: dvhltc@us.ibm.com CC: niv@us.ibm.com CC: tglx@linutronix.de CC: peterz@infradead.org CC: rostedt@goodmis.org CC: Valdis.Kletnieks@vt.edu CC: dhowells@redhat.com CC: eric.dumazet@gmail.com CC: Alexey Dobriyan <adobriyan@gmail.com> Signed-off-by:
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Arnd Bergmann authored
This adds annotations for RCU operations in core kernel components Signed-off-by:
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Arnd Bergmann authored
Signed-off-by:
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Arnd Bergmann authored
Signed-off-by:
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Arnd Bergmann authored
Signed-off-by:
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Paul E. McKenney authored
Make it explicit that new RCU read-side critical sections that start after call_rcu() and synchronize_rcu() start might still be running after the end of the relevant grace period. Signed-off-by:
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Paul E. McKenney authored
Although the RCU CPU stall warning messages are a very good way to alert people to a problem, once alerted, it is sometimes helpful to shut them off in order to avoid obscuring other messages that might be being used to track down the problem. Although you can rebuild the kernel with CONFIG_RCU_CPU_STALL_DETECTOR=n, this is sometimes inconvenient. This commit therefore adds a boot parameter named "rcu_cpu_stall_suppress" that shuts these messages off without requiring a rebuild (though a reboot might be needed for those not brave enough to patch their kernel while it is running). This message-suppression was already in place for the panic case, so this commit need only rename the variable and export it via module_param(). Signed-off-by: -
Paul E. McKenney authored
Also set the default to 60 seconds, up from the previous hard-coded timeout of 10 seconds. This allows people who care to set short timeouts, while avoiding people with unusual configurations (make randconfig!!!) from being bothered with spurious CPU stall warnings. Signed-off-by:
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Tetsuo Handa authored
find_task_by_vpid() says "Must be called under rcu_read_lock().". But due to commit 3120438a "rcu: Disable lockdep checking in RCU list-traversal primitives", we are currently unable to catch "find_task_by_vpid() with tasklist_lock held but RCU lock not held" errors due to the RCU-lockdep checks being suppressed in the RCU variants of the struct list_head traversals. This commit therefore places an explicit check for being in an RCU read-side critical section in find_task_by_pid_ns(). =================================================== [ INFO: suspicious rcu_dereference_check() usage. ] --------------------------------------------------- kernel/pid.c:386 invoked rcu_dereference_check() without protection! other info that might help us debug this: rcu_scheduler_active = 1, debug_locks = 1 1 lock held by rc.sysinit/1102: #0: (tasklist_lock){.+.+..}, at: [<c1048340>] sys_setpgid+0x40/0x160 stack backtrace: Pid: 1102, comm: rc.sysinit Not tainted 2.6.35-rc3-dirty #1 Call Trace: [<c105e714>] lockdep_rcu_dereference+0x94/0xb0 [<c104b4cd>] find_task_by_pid_ns+0x6d/0x70 [<c104b4e8>] find_task_by_vpid+0x18/0x20 [<c1048347>] sys_setpgid+0x47/0x160 [<c1002b50>] sysenter_do_call+0x12/0x36 Commit updated to use a new rcu_lockdep_assert() exported API rather than the old internal __do_rcu_dereference(). Signed-off-by:
Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by:
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Lai Jiangshan authored
&percpu_data is compatible with allocated percpu data. And we use it and remove the "->rda[NR_CPUS]" array, saving significant storage on systems with large numbers of CPUs. This does add an additional level of indirection and thus an additional cache line referenced, but because ->rda is not used on the read side, this is OK. Signed-off-by:
Lai Jiangshan <laijs@cn.fujitsu.com> Reviewed-by:
Tejun Heo <tj@kernel.org> Signed-off-by:
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Lai Jiangshan authored
Add random preemption to help we to torture the preemptable rcu. srcu_read_delay() also calls rcu_read_delay() for shorter delays. Added comment to preempt_schedule() call indicating that no quiescent states happen if preemption is disabled. Signed-off-by:
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Paul E. McKenney authored
Add a section describing PROVE_RCU, DEBUG_OBJECTS_RCU_HEAD, and the __rcu sparse checking to the RCU checklist. Suggested-by:
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Arnd Bergmann authored
Signed-off-by:
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Arnd Bergmann authored
Signed-off-by:
Patrick McHardy <kaber@trash.net> Cc: "David S. Miller" <davem@davemloft.net> Cc: Eric Dumazet <eric.dumazet@gmail.com> Reviewed-by:
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Arnd Bergmann authored
Signed-off-by:
Dmitry Torokhov <dtor@mail.ru> Reviewed-by:
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Arnd Bergmann authored
Signed-off-by:
Trond Myklebust <Trond.Myklebust@netapp.com>
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Arnd Bergmann authored
Signed-off-by:
David Howells <dhowells@redhat.com> Reviewed-by:
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Arnd Bergmann authored
Signed-off-by:
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Arnd Bergmann authored
Signed-off-by:
Paul Menage <menage@google.com> Cc: Li Zefan <lizf@cn.fujitsu.com> Reviewed-by:
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Arnd Bergmann authored
This avoids warnings from missing __rcu annotations in the rculist implementation, making it possible to use the same lists in both RCU and non-RCU cases. We can add rculist annotations later, together with lockdep support for rculist, which is missing as well, but that may involve changing all the users. Signed-off-by:
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Paul E. McKenney authored
This commit provides definitions for the __rcu annotation defined earlier. This annotation permits sparse to check for correct use of RCU-protected pointers. If a pointer that is annotated with __rcu is accessed directly (as opposed to via rcu_dereference(), rcu_assign_pointer(), or one of their variants), sparse can be made to complain. To enable such complaints, use the new default-disabled CONFIG_SPARSE_RCU_POINTER kernel configuration option. Please note that these sparse complaints are intended to be a debugging aid, -not- a code-style-enforcement mechanism. There are special rcu_dereference_protected() and rcu_access_pointer() accessors for use when RCU read-side protection is not required, for example, when no other CPU has access to the data structure in question or while the current CPU hold the update-side lock. This patch also updates a number of docbook comments that were showing their age. Signed-off-by:
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Paul E. McKenney authored
The task_cls_classid() function applies rcu_dereference() to integers, which does not work with the shiny new sparse-based checking in rcu_dereference(). This commit therefore moves to the new RCU API rcu_dereference_index_check(). Signed-off-by:
Herbert Xu <herbert@gondor.apana.org.au>
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- 18 Aug, 2010 1 commit
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git://git.linux-nfs.org/projects/trondmy/nfs-2.6Linus Torvalds authored
* 'bugfixes' of git://git.linux-nfs.org/projects/trondmy/nfs-2.6: NFS: Fix an Oops in the NFSv4 atomic open code NFS: Fix the selection of security flavours in Kconfig NFS: fix the return value of nfs_file_fsync() rpcrdma: Fix SQ size calculation when memreg is FRMR xprtrdma: Do not truncate iova_start values in frmr registrations. nfs: Remove redundant NULL check upon kfree() nfs: Add "lookupcache" to displayed mount options NFS: allow close-to-open cache semantics to apply to root of NFS filesystem SUNRPC: fix NFS client over TCP hangs due to packet loss (Bug 16494)
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