[PATCH 07/18] m68k: remove big kernel lock

[PATCH 07/18] m68k: remove big kernel lock

[Arnd Bergmann]

The cache flush code only locks against itself, so there
is no excuse to use the BKL here. This replaces it with
a local mutex in order to maintain serialization of flushes.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Roman Zippel <zippel@linux-m68k.org>
Cc: linux-m68k@lists.linux-m68k.org
---
 arch/m68k/kernel/sys_m68k.c |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/m68k/kernel/sys_m68k.c b/arch/m68k/kernel/sys_m68k.c
index 2f431ec..f6aec52 100644
--- a/arch/m68k/kernel/sys_m68k.c
+++ b/arch/m68k/kernel/sys_m68k.c
@@ -12,7 +12,7 @@
 #include <linux/mm.h>
 #include <linux/fs.h>
 #include <linux/smp.h>
-#include <linux/smp_lock.h>
+#include <linux/mutex.h>
 #include <linux/sem.h>
 #include <linux/msg.h>
 #include <linux/shm.h>
@@ -374,10 +374,11 @@ cache_flush_060 (unsigned long addr, int scope, int cache, unsigned long len)
 asmlinkage int
 sys_cacheflush (unsigned long addr, int scope, int cache, unsigned long len)
 {
+	static DEFINE_MUTEX(cacheflush_mutex);
 	struct vm_area_struct *vma;
 	int ret = -EINVAL;
 
-	lock_kernel();
+	mutex_lock(&cacheflush_mutex);
 	if (scope < FLUSH_SCOPE_LINE || scope > FLUSH_SCOPE_ALL ||
 	    cache & ~FLUSH_CACHE_BOTH)
 		goto out;
@@ -446,7 +447,7 @@ sys_cacheflush (unsigned long addr, int scope, int cache, unsigned long len)
 	    }
 	}
 out:
-	unlock_kernel();
+	mutex_unlock(&cacheflush_mutex);
 	return ret;
 }
 
-- 
1.7.1

Re: [PATCH 07/18] m68k: remove big kernel lock

[Andreas Schwab]

Arnd Bergmann <arnd@arndb.de> writes:

> The cache flush code only locks against itself, so there
> is no excuse to use the BKL here. This replaces it with
> a local mutex in order to maintain serialization of flushes.

I don't think this needs a lock at all.

Andreas.

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Re: [PATCH 07/18] m68k: remove big kernel lock

[Arnd Bergmann]

On Tuesday 21 September 2010, Andreas Schwab wrote:
> 
> Arnd Bergmann <arnd@arndb.de> writes:
> 
> > The cache flush code only locks against itself, so there
> > is no excuse to use the BKL here. This replaces it with
> > a local mutex in order to maintain serialization of flushes.
> 
> I don't think this needs a lock at all.
> 

Quite likely, I just took the most conservative approach.
If you want to queue a patch to drop the BKL from m68k, I'll
happily drop this one from my series.

	Arnd

Re: [PATCH 07/18] m68k: remove big kernel lock

[Geert Uytterhoeven]

On Wed, Sep 22, 2010 at 13:04, Arnd Bergmann <arnd@arndb.de> wrote:
> On Tuesday 21 September 2010, Andreas Schwab wrote:
>>
>> Arnd Bergmann <arnd@arndb.de> writes:
>>
>> > The cache flush code only locks against itself, so there
>> > is no excuse to use the BKL here. This replaces it with
>> > a local mutex in order to maintain serialization of flushes.
>>
>> I don't think this needs a lock at all.
>
> Quite likely, I just took the most conservative approach.
> If you want to queue a patch to drop the BKL from m68k, I'll
> happily drop this one from my series.

I'm dropping the locking completely. Patch will follow.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds