From: Benjamin Herrenschmidt Date: Sun, 14 Jun 2009 16:16:10 +0000 (+0000) Subject: powerpc: Add memory clobber to mtspr() X-Git-Tag: firefly_0821_release~13700^2~4 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=2fae0a524b193e200b71778407ad29b22417056a;p=firefly-linux-kernel-4.4.55.git powerpc: Add memory clobber to mtspr() Without this clobber, mtspr can be re-ordered by gcc vs. surrounding memory accesses. While this might be ok for some cases, it's not in others and I'm not confident that all callers get it right (In fact I'm sure some of them don't). So for now, let's make mtspr() itself contain a memory clobber until we can audit and fix everything, at which point we can remove it if we think it's worth doing so. Signed-off-by: Benjamin Herrenschmidt --- diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h index a3c28e46947c..1170267736d3 100644 --- a/arch/powerpc/include/asm/reg.h +++ b/arch/powerpc/include/asm/reg.h @@ -755,7 +755,8 @@ #define mfspr(rn) ({unsigned long rval; \ asm volatile("mfspr %0," __stringify(rn) \ : "=r" (rval)); rval;}) -#define mtspr(rn, v) asm volatile("mtspr " __stringify(rn) ",%0" : : "r" (v)) +#define mtspr(rn, v) asm volatile("mtspr " __stringify(rn) ",%0" : : "r" (v)\ + : "memory") #ifdef __powerpc64__ #ifdef CONFIG_PPC_CELL