Message ID | 20100413.005640.48990319.davem@davemloft.net |
---|---|
State | Not Applicable |
Delegated to: | David Miller |
Headers | show |
On Tue, 2010-04-13 at 00:56 -0700, David Miller wrote: > If we are in an NMI then doing a plain raw_local_irq_disable() will > write PIL_NORMAL_MAX into %pil, which is lower than PIL_NMI, and thus > we'll re-enable NMIs and recurse. > > Doing a simple: > > %pil = %pil | PIL_NORMAL_MAX > > does what we want, if we're already at PIL_NMI (15) we leave it at > that setting, else we set it to PIL_NORMAL_MAX (14). Ah indeed, and without a conditional, very nice! It does rely on the exact values of the PIL_levels, it might make sense to note that in the comment, something like: * Assumes: PIL_NMI | PIL_NORMAL_MAX == PIL_NMI. Hmm, it also assumes %pil is never anything other than 0, PIL_NORMAL_MAX, PIL_NMI, because if: (%pil & 1) && (%pil != PIL_NMI) then you'll end up disabling NMIs. Could something like that ever happen? -- To unsubscribe from this list: send the line "unsubscribe sparclinux" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
From: Peter Zijlstra <peterz@infradead.org> Date: Tue, 13 Apr 2010 10:37:14 +0200 > Hmm, it also assumes %pil is never anything other than 0, > PIL_NORMAL_MAX, PIL_NMI, because if: > > (%pil & 1) && (%pil != PIL_NMI) > > then you'll end up disabling NMIs. Could something like that ever > happen? The only values we ever program into the %pil are 0, PIL_NORMAL_MAX and PIL_NMI Since PIL_NMI is the largest %pil value and all bits are set in it (0xf), it doesn't matter what PIL_NORMAL_MAX actually is. Yes this all deserves a comment, I'll add one, thanks for pointing that out. -- To unsubscribe from this list: send the line "unsubscribe sparclinux" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/arch/sparc/include/asm/irqflags_64.h b/arch/sparc/include/asm/irqflags_64.h index 8b49bf9..a16e94c 100644 --- a/arch/sparc/include/asm/irqflags_64.h +++ b/arch/sparc/include/asm/irqflags_64.h @@ -76,9 +76,19 @@ static inline int raw_irqs_disabled(void) */ static inline unsigned long __raw_local_irq_save(void) { - unsigned long flags = __raw_local_save_flags(); + unsigned long flags, tmp; - raw_local_irq_disable(); + /* Disable interrupts to PIL_NORMAL_MAX unless we already + * are using PIL_NMI, in which case PIL_NMI is retained. + */ + __asm__ __volatile__( + "rdpr %%pil, %0\n\t" + "or %0, %2, %1\n\t" + "wrpr %1, 0x0, %%pil" + : "=r" (flags), "=r" (tmp) + : "i" (PIL_NORMAL_MAX) + : "memory" + ); return flags; }