Eric Lee / smarc-ti-linux-kernel

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Commit 64b47e8fdb40a0d46e8cf458dd3e24f8afa073f6

Authored by Josh Triplett
Committed by Linus Torvalds
1 parent 188a81409f
Exists in master and in 13 other branches dlt-processor-sdk-linux-03.00.00.04, processor-sdk-linux-02.00.01, smarc-ti-linux-3.15.y, smarc-ti-lsk-linux-4.1.y, smarct3x-processor-sdk-04.01.00.06, smarct3x-processor-sdk-linux-02.00.01, smarct3x-processor-sdk-linux-03.00.00.04, smarct4x-800-processor-sdk-linux-02.00.01, smarct4x-processor-sdk-04.01.00.06, smarct4x-processor-sdk-linux-02.00.01, smarct4x-processor-sdk-linux-03.00.00.04, ti-linux-3.15.y, ti-lsk-linux-4.1.y

lglock: map to spinlock when !CONFIG_SMP 

When the system has only one CPU, lglock is effectively a spinlock; map
it directly to spinlock to eliminate the indirection and duplicate code.

In addition to removing overhead, this drops 1.6k of code with a
defconfig modified to have !CONFIG_SMP, and 1.1k with a minimal config.

Signed-off-by: Josh Triplett <josh@joshtriplett.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Michal Marek <mmarek@suse.cz>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: David Howells <dhowells@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Nick Piggin <npiggin@kernel.dk>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Showing 2 changed files with 18 additions and 1 deletions Side-by-side Diff

include/linux/lglock.h
Diff comments   View file @ 64b47e8
... ... @@ -25,6 +25,8 @@
25 25 #include <linux/cpu.h>
26 26 #include <linux/notifier.h>
27 27  
  28 +#ifdef CONFIG_SMP
  29 +
28 30 #ifdef CONFIG_DEBUG_LOCK_ALLOC
29 31 #define LOCKDEP_INIT_MAP lockdep_init_map
30 32 #else
... ... @@ -56,6 +58,20 @@
56 58 void lg_local_unlock_cpu(struct lglock *lg, int cpu);
57 59 void lg_global_lock(struct lglock *lg);
58 60 void lg_global_unlock(struct lglock *lg);
  61 +
  62 +#else
  63 +/* When !CONFIG_SMP, map lglock to spinlock */
  64 +#define lglock spinlock
  65 +#define DEFINE_LGLOCK(name) DEFINE_SPINLOCK(name)
  66 +#define DEFINE_STATIC_LGLOCK(name) static DEFINE_SPINLOCK(name)
  67 +#define lg_lock_init(lg, name) spin_lock_init(lg)
  68 +#define lg_local_lock spin_lock
  69 +#define lg_local_unlock spin_unlock
  70 +#define lg_local_lock_cpu(lg, cpu) spin_lock(lg)
  71 +#define lg_local_unlock_cpu(lg, cpu) spin_unlock(lg)
  72 +#define lg_global_lock spin_lock
  73 +#define lg_global_unlock spin_unlock
  74 +#endif
59 75  
60 76 #endif
kernel/locking/Makefile
Diff comments   View file @ 64b47e8
1 1  
2   -obj-y += mutex.o semaphore.o rwsem.o lglock.o mcs_spinlock.o
  2 +obj-y += mutex.o semaphore.o rwsem.o mcs_spinlock.o
3 3  
4 4 ifdef CONFIG_FUNCTION_TRACER
5 5 CFLAGS_REMOVE_lockdep.o = -pg
... ... @@ -14,6 +14,7 @@
14 14 obj-$(CONFIG_LOCKDEP) += lockdep_proc.o
15 15 endif
16 16 obj-$(CONFIG_SMP) += spinlock.o
  17 +obj-$(CONFIG_SMP) += lglock.o
17 18 obj-$(CONFIG_PROVE_LOCKING) += spinlock.o
18 19 obj-$(CONFIG_RT_MUTEXES) += rtmutex.o
19 20 obj-$(CONFIG_DEBUG_RT_MUTEXES) += rtmutex-debug.o