Messages in this thread Patch in this message | | | Date | Wed, 19 Mar 2014 16:27:29 -0700 | From | Andrew Morton <> | Subject | Re: linux-next: manual merge of the akpm-current tree with the tip tree |
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On Mon, 17 Mar 2014 10:36:02 +0100 Peter Zijlstra <peterz@infradead.org> wrote:
> On Mon, Mar 17, 2014 at 08:31:24PM +1100, Stephen Rothwell wrote: > > Hi Andrew, > > > > Today's linux-next merge of the akpm-current tree got a conflict in > > kernel/locking/Makefile between commit fb0527bd5ea9 ("locking/mutexes: > > Introduce cancelable MCS lock for adaptive spinning") from the tree and > > commit 4dc0fe493027 ("lglock: map to spinlock when !CONFIG_SMP") from the > > akpm-current tree. > > > > I fixed it up (see below) and can carry the fix as necessary (no action > > is required). > > I'm a bit sad of not having seen that lglock patch at all.
Here 'tis:
From: Josh Triplett <josh@joshtriplett.org> Subject: 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> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> ---
include/linux/lglock.h | 16 ++++++++++++++++ kernel/locking/Makefile | 3 ++- 2 files changed, 18 insertions(+), 1 deletion(-)
diff -puN include/linux/lglock.h~lglock-map-to-spinlock-when-config_smp include/linux/lglock.h --- a/include/linux/lglock.h~lglock-map-to-spinlock-when-config_smp +++ a/include/linux/lglock.h @@ -25,6 +25,8 @@ #include <linux/cpu.h> #include <linux/notifier.h> +#ifdef CONFIG_SMP + #ifdef CONFIG_DEBUG_LOCK_ALLOC #define LOCKDEP_INIT_MAP lockdep_init_map #else @@ -57,4 +59,18 @@ void lg_local_unlock_cpu(struct lglock * void lg_global_lock(struct lglock *lg); void lg_global_unlock(struct lglock *lg); +#else +/* When !CONFIG_SMP, map lglock to spinlock */ +#define lglock spinlock +#define DEFINE_LGLOCK(name) DEFINE_SPINLOCK(name) +#define DEFINE_STATIC_LGLOCK(name) static DEFINE_SPINLOCK(name) +#define lg_lock_init(lg, name) spin_lock_init(lg) +#define lg_local_lock spin_lock +#define lg_local_unlock spin_unlock +#define lg_local_lock_cpu(lg, cpu) spin_lock(lg) +#define lg_local_unlock_cpu(lg, cpu) spin_unlock(lg) +#define lg_global_lock spin_lock +#define lg_global_unlock spin_unlock +#endif + #endif diff -puN kernel/locking/Makefile~lglock-map-to-spinlock-when-config_smp kernel/locking/Makefile --- a/kernel/locking/Makefile~lglock-map-to-spinlock-when-config_smp +++ a/kernel/locking/Makefile @@ -1,5 +1,5 @@ -obj-y += mutex.o semaphore.o rwsem.o lglock.o mcs_spinlock.o +obj-y += mutex.o semaphore.o rwsem.o mcs_spinlock.o ifdef CONFIG_FUNCTION_TRACER CFLAGS_REMOVE_lockdep.o = -pg @@ -14,6 +14,7 @@ ifeq ($(CONFIG_PROC_FS),y) obj-$(CONFIG_LOCKDEP) += lockdep_proc.o endif obj-$(CONFIG_SMP) += spinlock.o +obj-$(CONFIG_SMP) += lglock.o obj-$(CONFIG_PROVE_LOCKING) += spinlock.o obj-$(CONFIG_RT_MUTEXES) += rtmutex.o obj-$(CONFIG_DEBUG_RT_MUTEXES) += rtmutex-debug.o _
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