Commit-ID: 4544ba8c6b1743499cabb682897a469911845f15 Gitweb: http://git.kernel.org/tip/4544ba8c6b1743499cabb682897a469911845f15 Author: Borislav Petkov <b...@suse.de> AuthorDate: Mon, 16 May 2016 11:34:28 +0200 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Mon, 16 May 2016 12:35:40 +0200
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 <torva...@linux-foundation.org> Signed-off-by: Borislav Petkov <b...@suse.de> Cc: Alexander Shishkin <alexander.shish...@linux.intel.com> Cc: Andy Lutomirski <l...@amacapital.net> Cc: Arnaldo Carvalho de Melo <a...@redhat.com> Cc: Borislav Petkov <b...@alien8.de> Cc: Brian Gerst <brge...@gmail.com> Cc: Denys Vlasenko <dvlas...@redhat.com> Cc: Guenter Roeck <li...@roeck-us.net> Cc: H. Peter Anvin <h...@zytor.com> Cc: Jiri Olsa <jo...@redhat.com> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Stephane Eranian <eran...@google.com> Cc: Thomas Gleixner <t...@linutronix.de> Cc: Vince Weaver <vincent.wea...@maine.edu> Cc: linux-n...@vger.kernel.org Link: http://lkml.kernel.org/r/20160516093428.ga26...@pd.tnic Signed-off-by: Ingo Molnar <mi...@kernel.org> --- arch/x86/lib/rwsem.S | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/arch/x86/lib/rwsem.S b/arch/x86/lib/rwsem.S index a37462a..bf2c607 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 \
