From 93a6d3ce6962044fe9badf528fed46b455d58292 Mon Sep 17 00:00:00 2001 From: Paul Mackerras Date: Fri, 9 Jan 2009 16:52:19 +1100 Subject: powerpc: Provide a way to defer perf counter work until interrupts are enabled Because 64-bit powerpc uses lazy (soft) interrupt disabling, it is possible for a performance monitor exception to come in when the kernel thinks interrupts are disabled (i.e. when they are soft-disabled but hard-enabled). In such a situation the performance monitor exception handler might have some processing to do (such as process wakeups) which can't be done in what is effectively an NMI handler. This provides a way to defer that work until interrupts get enabled, either in raw_local_irq_restore() or by returning from an interrupt handler to code that had interrupts enabled. We have a per-processor flag that indicates that there is work pending to do when interrupts subsequently get re-enabled. This flag is checked in the interrupt return path and in raw_local_irq_restore(), and if it is set, perf_counter_do_pending() is called to do the pending work. Signed-off-by: Paul Mackerras --- arch/powerpc/kernel/asm-offsets.c | 1 + arch/powerpc/kernel/entry_64.S | 9 +++++++++ arch/powerpc/kernel/irq.c | 10 ++++++++++ 3 files changed, 20 insertions(+) (limited to 'arch/powerpc/kernel') diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c index 661d07d2146b..cea462900119 100644 --- a/arch/powerpc/kernel/asm-offsets.c +++ b/arch/powerpc/kernel/asm-offsets.c @@ -127,6 +127,7 @@ int main(void) DEFINE(PACAKMSR, offsetof(struct paca_struct, kernel_msr)); DEFINE(PACASOFTIRQEN, offsetof(struct paca_struct, soft_enabled)); DEFINE(PACAHARDIRQEN, offsetof(struct paca_struct, hard_enabled)); + DEFINE(PACAPERFPEND, offsetof(struct paca_struct, perf_counter_pending)); DEFINE(PACASLBCACHE, offsetof(struct paca_struct, slb_cache)); DEFINE(PACASLBCACHEPTR, offsetof(struct paca_struct, slb_cache_ptr)); DEFINE(PACACONTEXTID, offsetof(struct paca_struct, context.id)); diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S index 383ed6eb0085..f30b4e553c53 100644 --- a/arch/powerpc/kernel/entry_64.S +++ b/arch/powerpc/kernel/entry_64.S @@ -526,6 +526,15 @@ ALT_FW_FTR_SECTION_END_IFCLR(FW_FEATURE_ISERIES) 2: TRACE_AND_RESTORE_IRQ(r5); +#ifdef CONFIG_PERF_COUNTERS + /* check paca->perf_counter_pending if we're enabling ints */ + lbz r3,PACAPERFPEND(r13) + and. r3,r3,r5 + beq 27f + bl .perf_counter_do_pending +27: +#endif /* CONFIG_PERF_COUNTERS */ + /* extract EE bit and use it to restore paca->hard_enabled */ ld r3,_MSR(r1) rldicl r4,r3,49,63 /* r0 = (r3 >> 15) & 1 */ diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c index ac222d0ab12e..4efb886ea439 100644 --- a/arch/powerpc/kernel/irq.c +++ b/arch/powerpc/kernel/irq.c @@ -104,6 +104,13 @@ static inline notrace void set_soft_enabled(unsigned long enable) : : "r" (enable), "i" (offsetof(struct paca_struct, soft_enabled))); } +#ifdef CONFIG_PERF_COUNTERS +notrace void __weak perf_counter_do_pending(void) +{ + set_perf_counter_pending(0); +} +#endif + notrace void raw_local_irq_restore(unsigned long en) { /* @@ -135,6 +142,9 @@ notrace void raw_local_irq_restore(unsigned long en) iseries_handle_interrupts(); } + if (get_perf_counter_pending()) + perf_counter_do_pending(); + /* * if (get_paca()->hard_enabled) return; * But again we need to take care that gcc gets hard_enabled directly -- cgit v1.2.2