diff options
| author | Borislav Petkov <bp@suse.de> | 2016-05-16 11:34:28 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2016-05-16 12:35:40 +0200 |
| commit | 4544ba8c6b1743499cabb682897a469911845f15 (patch) | |
| tree | e3a1aa6b3d0036b8cd96dd031dd6f970a9cd525a /arch/x86 | |
| parent | 04cafed7fc19a8010771c788708ac97c405fc3de (diff) | |
locking/rwsem: Fix comment on register clobbering
Document explicitly that %edx can get clobbered on the slow path, on
32-bit kernels. Something I learned the hard way. :-\
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: linux-next@vger.kernel.org
Link: http://lkml.kernel.org/r/20160516093428.GA26108@pd.tnic
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/lib/rwsem.S | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/arch/x86/lib/rwsem.S b/arch/x86/lib/rwsem.S index a37462a23546..bf2c6074efd2 100644 --- a/arch/x86/lib/rwsem.S +++ b/arch/x86/lib/rwsem.S @@ -29,8 +29,10 @@ * there is contention on the semaphore. * * %eax contains the semaphore pointer on entry. Save the C-clobbered - * registers (%eax, %edx and %ecx) except %eax whish is either a return - * value or just clobbered.. + * registers (%eax, %edx and %ecx) except %eax which is either a return + * value or just gets clobbered. Same is true for %edx so make sure GCC + * reloads it after the slow path, by making it hold a temporary, for + * example see ____down_write(). */ #define save_common_regs \ |