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| author | Chris Metcalf <cmetcalf@tilera.com> | 2013-04-09 18:33:07 +0200 |
|---|---|---|
| committer | Chris Metcalf <cmetcalf@tilera.com> | 2013-04-09 18:33:07 +0200 |
| commit | ffae3d0e3606b2e274c9ec1b969342d630b2ecae (patch) | |
| tree | 8dbe20e674f88fa4b19a960a36ba45edef15bc86 /arch | |
| parent | tile: ns2cycles should use __raw_get_cpu_var (diff) | |
| download | linux-ffae3d0e3606b2e274c9ec1b969342d630b2ecae.tar.xz linux-ffae3d0e3606b2e274c9ec1b969342d630b2ecae.zip | |
tile: comment assumption about __insn_mtspr for <asm/irqflags.h>
The arch_local_irq_save(), etc., routines are required to function
as compiler barriers. They do, but it's subtle and requires knowing
that the gcc builtin __insn_mtspr() is marked as a memory clobber.
Provide a comment explaining the assumption.
Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/tile/include/asm/irqflags.h | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/arch/tile/include/asm/irqflags.h b/arch/tile/include/asm/irqflags.h index 241c0bb60b12..c96f9bbb760d 100644 --- a/arch/tile/include/asm/irqflags.h +++ b/arch/tile/include/asm/irqflags.h @@ -40,7 +40,15 @@ #include <asm/percpu.h> #include <arch/spr_def.h> -/* Set and clear kernel interrupt masks. */ +/* + * Set and clear kernel interrupt masks. + * + * NOTE: __insn_mtspr() is a compiler builtin marked as a memory + * clobber. We rely on it being equivalent to a compiler barrier in + * this code since arch_local_irq_save() and friends must act as + * compiler barriers. This compiler semantic is baked into enough + * places that the compiler will maintain it going forward. + */ #if CHIP_HAS_SPLIT_INTR_MASK() #if INT_PERF_COUNT < 32 || INT_AUX_PERF_COUNT < 32 || INT_MEM_ERROR >= 32 # error Fix assumptions about which word various interrupts are in |