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From: Andrew Morton <akpm@linux-foundation.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>,
	Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>,
	"H. Peter Anvin" <hpa@zytor.com>,
	linux-next@vger.kernel.org, linux-kernel@vger.kernel.org,
	Josh Triplett <josh@joshtriplett.org>
Subject: Re: linux-next: manual merge of the akpm-current tree with the tip tree
Date: Wed, 19 Mar 2014 16:27:29 -0700
Message-ID: <20140319162729.9b9f322b171140548b25c7af@linux-foundation.org> (raw)
In-Reply-To: <20140317093602.GY27965@twins.programming.kicks-ass.net>

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
_

  reply index

Thread overview: 87+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-03-17  9:31 Stephen Rothwell
2014-03-17  9:36 ` Peter Zijlstra
2014-03-19 23:27   ` Andrew Morton [this message]
  -- strict thread matches above, loose matches on Subject: below --
2019-10-31  5:43 Stephen Rothwell
2019-06-24 10:24 Stephen Rothwell
2019-05-01 11:10 Stephen Rothwell
2019-01-31  4:31 Stephen Rothwell
2018-08-20  4:32 Stephen Rothwell
2018-08-20 19:52 ` Andrew Morton
2018-03-23  5:59 Stephen Rothwell
2017-12-18  5:04 Stephen Rothwell
2017-11-10  4:33 Stephen Rothwell
2017-11-02  7:19 Stephen Rothwell
2017-08-22  6:57 Stephen Rothwell
2017-08-23  6:39 ` Vlastimil Babka
2017-08-11  7:53 Stephen Rothwell
2017-08-11  9:34 ` Peter Zijlstra
2017-08-11 10:48   ` Peter Zijlstra
2017-08-11 11:45   ` Stephen Rothwell
2017-08-11 11:56     ` Ingo Molnar
2017-08-11 12:17       ` Peter Zijlstra
2017-08-11 12:44         ` Ingo Molnar
2017-08-11 13:49           ` Stephen Rothwell
2017-08-11 14:04       ` Peter Zijlstra
2017-08-13  6:06         ` Nadav Amit
2017-08-13 12:50           ` Peter Zijlstra
2017-08-14  3:16             ` Minchan Kim
2017-08-14  5:07               ` Nadav Amit
2017-08-14  5:23                 ` Minchan Kim
2017-08-14  8:38                 ` Minchan Kim
2017-08-14 19:57                   ` Peter Zijlstra
2017-08-16  4:14                     ` Minchan Kim
2017-08-14 19:38                 ` Peter Zijlstra
2017-08-15  7:51                   ` Nadav Amit
2017-08-14  3:09         ` Minchan Kim
2017-08-14 18:54           ` Peter Zijlstra
2017-04-12  6:46 Stephen Rothwell
2017-04-12 20:53 ` Vlastimil Babka
2017-04-20  2:17   ` NeilBrown
2017-03-24  5:25 Stephen Rothwell
2017-02-17  4:40 Stephen Rothwell
2016-11-14  6:08 Stephen Rothwell
2016-07-29  4:14 Stephen Rothwell
2016-06-15  5:23 Stephen Rothwell
2016-06-18 19:39 ` Manfred Spraul
2016-04-29  6:12 Stephen Rothwell
2016-04-29  6:26 ` Ingo Molnar
2016-03-02  5:40 Stephen Rothwell
2016-02-26  5:07 Stephen Rothwell
2016-02-26 21:35 ` Andrew Morton
2016-02-19  4:09 Stephen Rothwell
2016-02-19 15:26 ` Ard Biesheuvel
2015-12-07  8:06 Stephen Rothwell
2015-10-02  4:21 Stephen Rothwell
2015-07-28  6:00 Stephen Rothwell
2015-07-29 17:12 ` Andrea Arcangeli
2015-07-29 17:47   ` Andy Lutomirski
2015-07-29 18:46     ` Thomas Gleixner
2015-07-30 15:38       ` Andrea Arcangeli
2015-07-29 23:06   ` Stephen Rothwell
2015-07-29 23:07     ` Thomas Gleixner
2015-09-07 23:35   ` Stephen Rothwell
2015-09-08 18:11     ` Linus Torvalds
2015-09-08 22:56       ` Stephen Rothwell
2015-09-08 23:03         ` Linus Torvalds
2015-09-08 23:21           ` Andrew Morton
2015-09-16  6:58             ` Geert Uytterhoeven
2015-06-04 12:07 Stephen Rothwell
2015-04-08  8:28 Stephen Rothwell
2015-04-08  8:25 Stephen Rothwell
2014-01-14  4:53 Stephen Rothwell
2014-01-14  5:04 ` Davidlohr Bueso
2014-01-14 12:51 ` Peter Zijlstra
2014-01-14 13:17   ` Geert Uytterhoeven
2014-01-14 13:33     ` Peter Zijlstra
2014-01-14 16:19     ` H. Peter Anvin
2014-01-14 15:15   ` H. Peter Anvin
2014-01-14 15:20     ` Geert Uytterhoeven
2014-01-14 15:41       ` Peter Zijlstra
2014-01-14 15:48         ` H. Peter Anvin
2014-01-07  6:00 Stephen Rothwell
2014-01-07  6:34 ` Tang Chen
2013-11-08  7:48 Stephen Rothwell
2013-11-08 18:58 ` Josh Triplett
2013-11-08 23:20   ` Stephen Rothwell
2013-11-09  0:19     ` Josh Triplett
2013-10-30  6:40 Stephen Rothwell

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