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arch/alpha/kernel/alpha_ksyms.c

@@ -40,7 +40,6 @@
 extern struct hwrpb_struct *hwrpb;
 extern void dump_thread(struct pt_regs *, struct user *);
 extern int dump_fpu(struct pt_regs *, elf_fpregset_t *);
-extern spinlock_t kernel_flag;
 extern spinlock_t rtc_lock;
 
 /* these are C runtime functions with special calling conventions: */
@@ -207,7 +206,6 @@ EXPORT_SYMBOL(up);
  */
 
 #ifdef CONFIG_SMP
-EXPORT_SYMBOL(kernel_flag);
 EXPORT_SYMBOL(synchronize_irq);
 EXPORT_SYMBOL(flush_tlb_all);
 EXPORT_SYMBOL(flush_tlb_mm);

arch/alpha/kernel/smp.c

@@ -67,8 +67,6 @@ enum ipi_message_type {
 	IPI_CPU_STOP,
 };
 
-spinlock_t kernel_flag __cacheline_aligned_in_smp = SPIN_LOCK_UNLOCKED;
-
 /* Set to a secondary's cpuid when it comes online.  */
 static int smp_secondary_alive __initdata = 0;
 

arch/arm/kernel/armksyms.c

@@ -273,7 +273,3 @@ EXPORT_SYMBOL_NOVERS(__down_trylock_failed);
 EXPORT_SYMBOL_NOVERS(__up_wakeup);
 
 EXPORT_SYMBOL(get_wchan);
-
-#ifdef CONFIG_PREEMPT
-EXPORT_SYMBOL(kernel_flag);
-#endif

arch/arm/kernel/setup.c

@@ -36,10 +36,6 @@
 #define MEM_SIZE	(16*1024*1024)
 #endif
 
-#ifdef CONFIG_PREEMPT
-spinlock_t kernel_flag __cacheline_aligned_in_smp = SPIN_LOCK_UNLOCKED;
-#endif
-
 #if defined(CONFIG_FPE_NWFPE) || defined(CONFIG_FPE_FASTFPE)
 char fpe_type[8];
 

arch/i386/kernel/i386_ksyms.c

@@ -126,7 +126,6 @@ EXPORT_SYMBOL(mmx_copy_page);
 
 #ifdef CONFIG_SMP
 EXPORT_SYMBOL(cpu_data);
-EXPORT_SYMBOL(kernel_flag);
 EXPORT_SYMBOL(cpu_online_map);
 EXPORT_SYMBOL_NOVERS(__write_lock_failed);
 EXPORT_SYMBOL_NOVERS(__read_lock_failed);

arch/i386/kernel/smp.c

@@ -18,6 +18,7 @@
 #include <linux/kernel_stat.h>
 #include <linux/mc146818rtc.h>
 #include <linux/cache.h>
+#include <linux/interrupt.h>
 
 #include <asm/mtrr.h>
 #include <asm/pgalloc.h>
@@ -103,9 +104,6 @@
  *	about nothing of note with C stepping upwards.
  */
 
-/* The 'big kernel lock' */
-spinlock_t kernel_flag __cacheline_aligned_in_smp = SPIN_LOCK_UNLOCKED;
-
 struct tlb_state cpu_tlbstate[NR_CPUS] __cacheline_aligned = {[0 ... NR_CPUS-1] = { &init_mm, 0, }};
 
 /*

arch/ia64/kernel/ia64_ksyms.c

@@ -84,10 +84,6 @@ EXPORT_SYMBOL(smp_call_function);
 EXPORT_SYMBOL(smp_call_function_single);
 EXPORT_SYMBOL(cpu_online_map);
 EXPORT_SYMBOL(ia64_cpu_to_sapicid);
-
-#include <asm/smplock.h>
-EXPORT_SYMBOL(kernel_flag);
-
 #else /* !CONFIG_SMP */
 
 EXPORT_SYMBOL(__flush_tlb_all);

arch/ia64/kernel/smp.c

@@ -52,14 +52,6 @@
 #include <asm/unistd.h>
 #include <asm/mca.h>
 
-/*
- * The Big Kernel Lock.  It's not supposed to be used for performance critical stuff
- * anymore.  But we still need to align it because certain workloads are still affected by
- * it.  For example, llseek() and various other filesystem related routines still use the
- * BKL.
- */
-spinlock_t kernel_flag __cacheline_aligned = SPIN_LOCK_UNLOCKED;
-
 /*
  * Structure and data for smp_call_function(). This is designed to minimise static memory
  * requirements. It also looks cleaner.

arch/mips/kernel/smp.c

@@ -53,7 +53,6 @@
 
 
 /* Ze Big Kernel Lock! */
-spinlock_t kernel_flag __cacheline_aligned_in_smp = SPIN_LOCK_UNLOCKED;
 int smp_threads_ready;  /* Not used */
 int smp_num_cpus;    
 int global_irq_holder = NO_PROC_ID;

arch/mips64/kernel/smp.c

@@ -53,7 +53,6 @@ static void sendintr(int destid, unsigned char status)
 #endif /* CONFIG_SGI_IP27 */
 
 /* The 'big kernel lock' */
-spinlock_t kernel_flag __cacheline_aligned_in_smp = SPIN_LOCK_UNLOCKED;
 int smp_threads_ready;	/* Not used */
 atomic_t smp_commenced = ATOMIC_INIT(0);
 struct cpuinfo_mips cpu_data[NR_CPUS];

arch/parisc/kernel/parisc_ksyms.c

@@ -35,9 +35,6 @@ EXPORT_SYMBOL(boot_cpu_data);
 #ifdef CONFIG_SMP
 EXPORT_SYMBOL(synchronize_irq);
 
-#include <asm/smplock.h>
-EXPORT_SYMBOL(kernel_flag);
-
 #include <asm/system.h>
 EXPORT_SYMBOL(__global_sti);
 EXPORT_SYMBOL(__global_cli);

arch/ppc/kernel/ppc_ksyms.c

@@ -93,9 +93,6 @@ EXPORT_SYMBOL(enable_irq);
 EXPORT_SYMBOL(disable_irq);
 EXPORT_SYMBOL(disable_irq_nosync);
 EXPORT_SYMBOL(probe_irq_mask);
-#ifdef CONFIG_SMP
-EXPORT_SYMBOL(kernel_flag);
-#endif /* CONFIG_SMP */
 
 EXPORT_SYMBOL(ISA_DMA_THRESHOLD);
 EXPORT_SYMBOL_NOVERS(DMA_MODE_READ);

arch/ppc/kernel/smp.c

@@ -47,7 +47,6 @@ struct cpuinfo_PPC cpu_data[NR_CPUS];
 struct klock_info_struct klock_info = { KLOCK_CLEAR, 0 };
 atomic_t ipi_recv;
 atomic_t ipi_sent;
-spinlock_t kernel_flag __cacheline_aligned_in_smp = SPIN_LOCK_UNLOCKED;
 unsigned int prof_multiplier[NR_CPUS] = { [1 ... NR_CPUS-1] = 1 };
 unsigned int prof_counter[NR_CPUS] = { [1 ... NR_CPUS-1] = 1 };
 unsigned long cache_decay_ticks = HZ/100;

arch/ppc64/kernel/ppc_ksyms.c

@@ -74,7 +74,6 @@ EXPORT_SYMBOL(disable_irq);
 EXPORT_SYMBOL(disable_irq_nosync);
 #ifdef CONFIG_SMP
 EXPORT_SYMBOL(synchronize_irq);
-EXPORT_SYMBOL(kernel_flag);
 #endif /* CONFIG_SMP */
 
 EXPORT_SYMBOL(register_ioctl32_conversion);

arch/ppc64/kernel/smp.c

@@ -51,7 +51,6 @@
 #include <asm/machdep.h>
 
 int smp_threads_ready = 0;
-spinlock_t kernel_flag __cacheline_aligned = SPIN_LOCK_UNLOCKED;
 unsigned long cache_decay_ticks;
 
 /* initialised so it doesnt end up in bss */

arch/s390/kernel/smp.c

@@ -54,8 +54,6 @@ cycles_t         cacheflush_time=0;
 int              smp_threads_ready=0;      /* Set when the idlers are all forked. */
 static atomic_t  smp_commenced = ATOMIC_INIT(0);
 
-spinlock_t       kernel_flag __cacheline_aligned_in_smp = SPIN_LOCK_UNLOCKED;
-
 volatile unsigned long phys_cpu_present_map;
 volatile unsigned long cpu_online_map;
 unsigned long    cache_decay_ticks = 0;
@@ -634,7 +632,6 @@ int setup_profiling_timer(unsigned int multiplier)
 }
 
 EXPORT_SYMBOL(lowcore_ptr);
-EXPORT_SYMBOL(kernel_flag);
 EXPORT_SYMBOL(smp_ctl_set_bit);
 EXPORT_SYMBOL(smp_ctl_clear_bit);
 EXPORT_SYMBOL(smp_num_cpus);

arch/s390x/kernel/smp.c

@@ -53,8 +53,6 @@ cycles_t         cacheflush_time=0;
 int              smp_threads_ready=0;      /* Set when the idlers are all forked. */
 static atomic_t  smp_commenced = ATOMIC_INIT(0);
 
-spinlock_t       kernel_flag __cacheline_aligned_in_smp = SPIN_LOCK_UNLOCKED;
-
 volatile unsigned long phys_cpu_present_map;
 volatile unsigned long cpu_online_map;
 unsigned long    cache_decay_ticks = 0;
@@ -613,7 +611,6 @@ int setup_profiling_timer(unsigned int multiplier)
 }
 
 EXPORT_SYMBOL(lowcore_ptr);
-EXPORT_SYMBOL(kernel_flag);
 EXPORT_SYMBOL(smp_ctl_set_bit);
 EXPORT_SYMBOL(smp_ctl_clear_bit);
 EXPORT_SYMBOL(smp_num_cpus);

arch/sparc/kernel/smp.c

@@ -66,9 +66,6 @@ cycles_t cacheflush_time = 0; /* XXX */
  * instruction which is much better...
  */
 
-/* Kernel spinlock */
-spinlock_t kernel_flag __cacheline_aligned_in_smp = SPIN_LOCK_UNLOCKED;
-
 /* Used to make bitops atomic */
 unsigned char bitops_spinlock = 0;
 

arch/sparc/kernel/sparc_ksyms.c

@@ -77,10 +77,6 @@ extern int __divdi3(int, int);
 
 extern void dump_thread(struct pt_regs *, struct user *);
 
-#ifdef CONFIG_SMP
-extern spinlock_t kernel_flag;
-#endif
-
 /* One thing to note is that the way the symbols of the mul/div
  * support routines are named is a mess, they all start with
  * a '.' which makes it a bitch to export, here is the trick:
@@ -130,9 +126,6 @@ EXPORT_SYMBOL_PRIVATE(_clear_bit);
 EXPORT_SYMBOL_PRIVATE(_change_bit);
 
 #ifdef CONFIG_SMP
-/* Kernel wide locking */
-EXPORT_SYMBOL(kernel_flag);
-
 /* IRQ implementation. */
 EXPORT_SYMBOL(global_irq_holder);
 EXPORT_SYMBOL(synchronize_irq);

arch/sparc64/kernel/smp.c

@@ -46,9 +46,6 @@ cpuinfo_sparc cpu_data[NR_CPUS];
 /* Please don't make this stuff initdata!!!  --DaveM */
 static unsigned char boot_cpu_id;
 
-/* Kernel spinlock */
-spinlock_t kernel_flag __cacheline_aligned_in_smp = SPIN_LOCK_UNLOCKED;
-
 atomic_t sparc64_num_cpus_online = ATOMIC_INIT(0);
 unsigned long cpu_online_map = 0;
 atomic_t sparc64_num_cpus_possible = ATOMIC_INIT(0);

arch/sparc64/kernel/sparc64_ksyms.c

@@ -101,9 +101,7 @@ extern int __ashrdi3(int, int);
 extern void dump_thread(struct pt_regs *, struct user *);
 extern int dump_fpu (struct pt_regs * regs, elf_fpregset_t * fpregs);
 
-#ifdef CONFIG_SMP
-extern spinlock_t kernel_flag;
-#ifdef CONFIG_DEBUG_SPINLOCK
+#if defined(CONFIG_SMP) && defined(CONFIG_DEBUG_SPINLOCK)
 extern void _do_spin_lock (spinlock_t *lock, char *str);
 extern void _do_spin_unlock (spinlock_t *lock);
 extern int _spin_trylock (spinlock_t *lock);
@@ -112,7 +110,6 @@ extern void _do_read_unlock(rwlock_t *rw, char *str);
 extern void _do_write_lock(rwlock_t *rw, char *str);
 extern void _do_write_unlock(rwlock_t *rw);
 #endif
-#endif
 
 extern unsigned long phys_base;
 extern unsigned long pfn_base;
@@ -127,9 +124,6 @@ EXPORT_SYMBOL(__write_lock);
 EXPORT_SYMBOL(__write_unlock);
 #endif
 
-/* Kernel wide locking */
-EXPORT_SYMBOL(kernel_flag);
-
 /* Hard IRQ locking */
 #ifdef CONFIG_SMP
 EXPORT_SYMBOL(synchronize_irq);

arch/x86_64/kernel/smp.c

@@ -22,9 +22,6 @@
 #include <asm/pgalloc.h>
 #include <asm/tlbflush.h>
 
-/* The 'big kernel lock' */
-spinlock_t kernel_flag __cacheline_aligned_in_smp = SPIN_LOCK_UNLOCKED;
-
 /*
  * the following functions deal with sending IPIs between CPUs.
  *

arch/x86_64/kernel/x8664_ksyms.c

@@ -109,7 +109,6 @@ EXPORT_SYMBOL(mmx_copy_page);
 
 #ifdef CONFIG_SMP
 EXPORT_SYMBOL(cpu_data);
-EXPORT_SYMBOL(kernel_flag);
 EXPORT_SYMBOL(smp_num_cpus);
 EXPORT_SYMBOL(cpu_online_map);
 EXPORT_SYMBOL_NOVERS(__write_lock_failed);

include/linux/smp_lock.h

@@ -2,21 +2,10 @@
 #define __LINUX_SMPLOCK_H
 
 #include <linux/config.h>
-
-#if !defined(CONFIG_SMP) && !defined(CONFIG_PREEMPT)
-
-#define lock_kernel()				do { } while(0)
-#define unlock_kernel()				do { } while(0)
-#define release_kernel_lock(task)		do { } while(0)
-#define reacquire_kernel_lock(task)		do { } while(0)
-#define kernel_locked() 1
-
-#else
-
-#include <linux/interrupt.h>
-#include <linux/spinlock.h>
 #include <linux/sched.h>
-#include <asm/current.h>
+#include <linux/spinlock.h>
+
+#if CONFIG_SMP || CONFIG_PREEMPT
 
 extern spinlock_t kernel_flag;
 
@@ -26,23 +15,22 @@ extern spinlock_t kernel_flag;
 #define put_kernel_lock()	spin_unlock(&kernel_flag)
 
 /*
- * Release global kernel lock and global interrupt lock
+ * Release global kernel lock.
  */
-#define release_kernel_lock(task)		\
-do {						\
-	if (unlikely(task->lock_depth >= 0))	\
-		put_kernel_lock();		\
-} while (0)
+static inline void release_kernel_lock(struct task_struct *task)
+{
+	if (unlikely(task->lock_depth >= 0))
+		put_kernel_lock();
+}
 
 /*
  * Re-acquire the kernel lock
  */
-#define reacquire_kernel_lock(task)		\
-do {						\
-	if (unlikely(task->lock_depth >= 0))	\
-		get_kernel_lock();		\
-} while (0)
-
+static inline void reacquire_kernel_lock(struct task_struct *task)
+{
+	if (unlikely(task->lock_depth >= 0))
+		get_kernel_lock();
+}
 
 /*
  * Getting the big kernel lock.
@@ -51,22 +39,29 @@ do {						\
  * so we only need to worry about other
  * CPU's.
  */
-static __inline__ void lock_kernel(void)
+static inline void lock_kernel(void)
 {
 	int depth = current->lock_depth+1;
-	if (!depth)
+	if (likely(!depth))
 		get_kernel_lock();
 	current->lock_depth = depth;
 }
 
-static __inline__ void unlock_kernel(void)
+static inline void unlock_kernel(void)
 {
-	if (current->lock_depth < 0)
+	if (unlikely(current->lock_depth < 0))
 		BUG();
-	if (--current->lock_depth < 0)
+	if (likely(--current->lock_depth < 0))
 		put_kernel_lock();
 }
 
-#endif /* CONFIG_SMP */
+#else
+
+#define lock_kernel()				do { } while(0)
+#define unlock_kernel()				do { } while(0)
+#define release_kernel_lock(task)		do { } while(0)
+#define reacquire_kernel_lock(task)		do { } while(0)
+#define kernel_locked()				1
 
-#endif
+#endif /* CONFIG_SMP || CONFIG_PREEMPT */
+#endif /* __LINUX_SMPLOCK_H */

kernel/ksyms.c

@@ -51,6 +51,7 @@
 #include <linux/buffer_head.h>
 #include <linux/root_dev.h>
 #include <linux/percpu.h>
+#include <linux/smp_lock.h>
 #include <asm/checksum.h>
 
 #if defined(CONFIG_PROC_FS)
@@ -481,6 +482,9 @@ EXPORT_SYMBOL_GPL(idle_cpu);
 #if CONFIG_SMP
 EXPORT_SYMBOL_GPL(set_cpus_allowed);
 #endif
+#if CONFIG_SMP || CONFIG_PREEMPT
+EXPORT_SYMBOL(kernel_flag);
+#endif
 EXPORT_SYMBOL(jiffies);
 EXPORT_SYMBOL(jiffies_64);
 EXPORT_SYMBOL(xtime);

kernel/sched.c

@@ -1881,7 +1881,6 @@ void __init init_idle(task_t *idle, int cpu)
 }
 
 #if CONFIG_SMP
-
 /*
  * This is how migration works:
  *
@@ -2070,6 +2069,20 @@ __init int migration_init(void)
 
 #endif
 
+#if CONFIG_SMP || CONFIG_PREEMPT
+/*
+ * The 'big kernel lock'
+ *
+ * This spinlock is taken and released recursively by lock_kernel()
+ * and unlock_kernel().  It is transparently dropped and reaquired
+ * over schedule().  It is used to protect legacy code that hasn't
+ * been migrated to a proper locking design yet.
+ *
+ * Don't use in new code.
+ */
+spinlock_t kernel_flag __cacheline_aligned_in_smp = SPIN_LOCK_UNLOCKED;
+#endif
+
 extern void init_timervecs(void);
 extern void timer_bh(void);
 extern void tqueue_bh(void);