Commit 4544ba8c authored May 16, 2016 by Borislav Petkov Committed by Ingo Molnar May 16, 2016

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>

parent 04cafed7

arch/x86/lib/rwsem.S

+4 −2

Original line number	Diff line number	Diff line
		@@ -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 \

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