I assume you will pick this up, but I thought I might as well record it in the bug report as well...
New fix from Linus. For the *real* problem this time, I assume. Bjørn
--- Begin Message ---On Tue, 13 Jul 2010, Linus Torvalds wrote: > On Tue, Jul 13, 2010 at 10:50 AM, Linus Torvalds > <torva...@linux-foundation.org> wrote: > > > > No, you didn't back-port it wrong. I just didn't fix the right part. I > > thought the PV code used xchg, not cmpxchg, so I only patched that. > > But cmpxchg has the exact same issue. > > > > Does this fix it? It appears to, thanks a lot. [git|v2.6.32.16] wea...@thelma:/scratch/kernel/2.6.32.16$ nm arch/x86/kernel/pvclock.o 0000000000000000 b last_value .. And it did boot too. > Btw, this second patch was a bit more aggressive than the first one, > and actually removes the "memory" clobber entirely, and the fake cast > of the target type. Without the cast gcc spews a fair amount of warnings. About four every time it hits the include file. Just for completeness' sake I attached the patch on top of 2.6.32.16 that I built with. -- | .''`. ** Debian GNU/Linux ** Peter Palfrader | : :' : The universal http://www.palfrader.org/ | `. `' Operating System | `- http://www.debian.org/diff --git a/arch/x86/include/asm/cmpxchg_64.h b/arch/x86/include/asm/cmpxchg_64.h index 52de72e..f0551c5 100644 --- a/arch/x86/include/asm/cmpxchg_64.h +++ b/arch/x86/include/asm/cmpxchg_64.h @@ -26,26 +26,26 @@ static inline unsigned long __xchg(unsigned long x, volatile void *ptr, switch (size) { case 1: asm volatile("xchgb %b0,%1" - : "=q" (x) - : "m" (*__xg(ptr)), "0" (x) + : "=q" (x), "+m" (*__xg(ptr)) + : "0" (x) : "memory"); break; case 2: asm volatile("xchgw %w0,%1" - : "=r" (x) - : "m" (*__xg(ptr)), "0" (x) + : "=r" (x), "+m" (*__xg(ptr)) + : "0" (x) : "memory"); break; case 4: asm volatile("xchgl %k0,%1" - : "=r" (x) - : "m" (*__xg(ptr)), "0" (x) + : "=r" (x), "+m" (*__xg(ptr)) + : "0" (x) : "memory"); break; case 8: asm volatile("xchgq %0,%1" - : "=r" (x) - : "m" (*__xg(ptr)), "0" (x) + : "=r" (x), "+m" (*__xg(ptr)) + : "0" (x) : "memory"); break; } @@ -66,28 +66,24 @@ static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old, unsigned long prev; switch (size) { case 1: - asm volatile(LOCK_PREFIX "cmpxchgb %b1,%2" - : "=a"(prev) - : "q"(new), "m"(*__xg(ptr)), "0"(old) - : "memory"); + asm volatile(LOCK_PREFIX "cmpxchgb %b2,%1" + : "=a"(prev), "+m" (*__xg(ptr)) + : "q"(new), "0"(old)); return prev; case 2: - asm volatile(LOCK_PREFIX "cmpxchgw %w1,%2" - : "=a"(prev) - : "r"(new), "m"(*__xg(ptr)), "0"(old) - : "memory"); + asm volatile(LOCK_PREFIX "cmpxchgw %w2,%1" + : "=a"(prev), "+m" (*__xg(ptr)) + : "r"(new), "0"(old)); return prev; case 4: - asm volatile(LOCK_PREFIX "cmpxchgl %k1,%2" - : "=a"(prev) - : "r"(new), "m"(*__xg(ptr)), "0"(old) - : "memory"); + asm volatile(LOCK_PREFIX "cmpxchgl %k2,%1" + : "=a"(prev), "+m" (*__xg(ptr)) + : "r"(new), "0"(old)); return prev; case 8: - asm volatile(LOCK_PREFIX "cmpxchgq %1,%2" - : "=a"(prev) - : "r"(new), "m"(*__xg(ptr)), "0"(old) - : "memory"); + asm volatile(LOCK_PREFIX "cmpxchgq %2,%1" + : "=a"(prev), "+m" (*__xg(ptr)) + : "r"(new), "0"(old)); return prev; } return old;
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