From patchwork Wed Apr 14 06:46:04 2010 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Paul Mackerras X-Patchwork-Id: 50125 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from bilbo.ozlabs.org (localhost [127.0.0.1]) by ozlabs.org (Postfix) with ESMTP id 29780B7E00 for ; Wed, 14 Apr 2010 16:46:15 +1000 (EST) Received: by ozlabs.org (Postfix) id 0CFB1B7D19; Wed, 14 Apr 2010 16:46:07 +1000 (EST) Delivered-To: linuxppc-dev@ozlabs.org Received: by ozlabs.org (Postfix, from userid 1003) id 09DEFB7D1B; Wed, 14 Apr 2010 16:46:07 +1000 (EST) Date: Wed, 14 Apr 2010 16:46:04 +1000 From: Paul Mackerras To: Benjamin Herrenschmidt , Ingo Molnar , Peter Zijlstra Subject: [PATCH] powerpc/perf_event: Fix oops due to perf_event_do_pending call Message-ID: <20100414064603.GA4714@drongo> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.5.20 (2009-06-14) Cc: linuxppc-dev@ozlabs.org, linux-kernel@vger.kernel.org, Anton Blanchard X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.13 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+patchwork-incoming=ozlabs.org@lists.ozlabs.org Anton Blanchard found that large POWER systems would occasionally crash in the exception exit path when profiling with perf_events. The symptom was that an interrupt would occur late in the exit path when the MSR[RI] (recoverable interrupt) bit was clear. Interrupts should be hard-disabled at this point but they were enabled. Because the interrupt was not recoverable the system panicked. The reason is that the exception exit path was calling perf_event_do_pending after hard-disabling interrupts, and perf_event_do_pending will re-enable interrupts. The simplest and cleanest fix for this is to use the same mechanism that 32-bit powerpc does, namely to cause a self-IPI by setting the decrementer to 1. This means we can remove the tests in the exception exit path and raw_local_irq_restore. This also makes sure that the call to perf_event_do_pending from timer_interrupt() happens within irq_enter/irq_exit. (Note that calling perf_event_do_pending from timer_interrupt does not mean that there is a possible 1/HZ latency; setting the decrementer to 1 ensures that the timer interrupt will happen immediately, i.e. within one timebase tick, which is a few nanoseconds or 10s of nanoseconds.) Signed-off-by: Paul Mackerras Cc: stable@kernel.org --- Ben, please put this in your tree of fixes to go to Linus for 2.6.34, since it fixes a potential panic. arch/powerpc/include/asm/hw_irq.h | 38 ------------------------ arch/powerpc/kernel/asm-offsets.c | 1 arch/powerpc/kernel/entry_64.S | 9 ----- arch/powerpc/kernel/irq.c | 6 --- arch/powerpc/kernel/time.c | 60 ++++++++++++++++++++++++++++++-------- 5 files changed, 48 insertions(+), 66 deletions(-) diff --git a/arch/powerpc/include/asm/hw_irq.h b/arch/powerpc/include/asm/hw_irq.h index 9f4c9d4..bd100fc 100644 --- a/arch/powerpc/include/asm/hw_irq.h +++ b/arch/powerpc/include/asm/hw_irq.h @@ -130,43 +130,5 @@ static inline int irqs_disabled_flags(unsigned long flags) */ struct irq_chip; -#ifdef CONFIG_PERF_EVENTS - -#ifdef CONFIG_PPC64 -static inline unsigned long test_perf_event_pending(void) -{ - unsigned long x; - - asm volatile("lbz %0,%1(13)" - : "=r" (x) - : "i" (offsetof(struct paca_struct, perf_event_pending))); - return x; -} - -static inline void set_perf_event_pending(void) -{ - asm volatile("stb %0,%1(13)" : : - "r" (1), - "i" (offsetof(struct paca_struct, perf_event_pending))); -} - -static inline void clear_perf_event_pending(void) -{ - asm volatile("stb %0,%1(13)" : : - "r" (0), - "i" (offsetof(struct paca_struct, perf_event_pending))); -} -#endif /* CONFIG_PPC64 */ - -#else /* CONFIG_PERF_EVENTS */ - -static inline unsigned long test_perf_event_pending(void) -{ - return 0; -} - -static inline void clear_perf_event_pending(void) {} -#endif /* CONFIG_PERF_EVENTS */ - #endif /* __KERNEL__ */ #endif /* _ASM_POWERPC_HW_IRQ_H */ diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c index 957ceb7..c09138d 100644 --- a/arch/powerpc/kernel/asm-offsets.c +++ b/arch/powerpc/kernel/asm-offsets.c @@ -133,7 +133,6 @@ 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_event_pending)); DEFINE(PACACONTEXTID, offsetof(struct paca_struct, context.id)); #ifdef CONFIG_PPC_MM_SLICES DEFINE(PACALOWSLICESPSIZE, offsetof(struct paca_struct, diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S index 07109d8..42e9d90 100644 --- a/arch/powerpc/kernel/entry_64.S +++ b/arch/powerpc/kernel/entry_64.S @@ -556,15 +556,6 @@ ALT_FW_FTR_SECTION_END_IFCLR(FW_FEATURE_ISERIES) 2: TRACE_AND_RESTORE_IRQ(r5); -#ifdef CONFIG_PERF_EVENTS - /* check paca->perf_event_pending if we're enabling ints */ - lbz r3,PACAPERFPEND(r13) - and. r3,r3,r5 - beq 27f - bl .perf_event_do_pending -27: -#endif /* CONFIG_PERF_EVENTS */ - /* 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 64f6f20..066bd31 100644 --- a/arch/powerpc/kernel/irq.c +++ b/arch/powerpc/kernel/irq.c @@ -53,7 +53,6 @@ #include #include #include -#include #include #include @@ -145,11 +144,6 @@ notrace void raw_local_irq_restore(unsigned long en) } #endif /* CONFIG_PPC_STD_MMU_64 */ - if (test_perf_event_pending()) { - clear_perf_event_pending(); - perf_event_do_pending(); - } - /* * if (get_paca()->hard_enabled) return; * But again we need to take care that gcc gets hard_enabled directly diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c index 1b16b9a..0441bbd 100644 --- a/arch/powerpc/kernel/time.c +++ b/arch/powerpc/kernel/time.c @@ -532,25 +532,60 @@ void __init iSeries_time_init_early(void) } #endif /* CONFIG_PPC_ISERIES */ -#if defined(CONFIG_PERF_EVENTS) && defined(CONFIG_PPC32) -DEFINE_PER_CPU(u8, perf_event_pending); +#ifdef CONFIG_PERF_EVENTS -void set_perf_event_pending(void) +/* + * 64-bit uses a byte in the PACA, 32-bit uses a per-cpu variable... + */ +#ifdef CONFIG_PPC64 +static inline unsigned long test_perf_event_pending(void) { - get_cpu_var(perf_event_pending) = 1; - set_dec(1); - put_cpu_var(perf_event_pending); + unsigned long x; + + asm volatile("lbz %0,%1(13)" + : "=r" (x) + : "i" (offsetof(struct paca_struct, perf_event_pending))); + return x; } +static inline void set_perf_event_pending_flag(void) +{ + asm volatile("stb %0,%1(13)" : : + "r" (1), + "i" (offsetof(struct paca_struct, perf_event_pending))); +} + +static inline void clear_perf_event_pending(void) +{ + asm volatile("stb %0,%1(13)" : : + "r" (0), + "i" (offsetof(struct paca_struct, perf_event_pending))); +} + +#else /* 32-bit */ + +DEFINE_PER_CPU(u8, perf_event_pending); + +#define set_perf_event_pending_flag() __get_cpu_var(perf_event_pending) = 1 #define test_perf_event_pending() __get_cpu_var(perf_event_pending) #define clear_perf_event_pending() __get_cpu_var(perf_event_pending) = 0 -#else /* CONFIG_PERF_EVENTS && CONFIG_PPC32 */ +#endif /* 32 vs 64 bit */ + +void set_perf_event_pending(void) +{ + preempt_disable(); + set_perf_event_pending_flag(); + set_dec(1); + preempt_enable(); +} + +#else /* CONFIG_PERF_EVENTS */ #define test_perf_event_pending() 0 #define clear_perf_event_pending() -#endif /* CONFIG_PERF_EVENTS && CONFIG_PPC32 */ +#endif /* CONFIG_PERF_EVENTS */ /* * For iSeries shared processors, we have to let the hypervisor @@ -582,10 +617,6 @@ void timer_interrupt(struct pt_regs * regs) set_dec(DECREMENTER_MAX); #ifdef CONFIG_PPC32 - if (test_perf_event_pending()) { - clear_perf_event_pending(); - perf_event_do_pending(); - } if (atomic_read(&ppc_n_lost_interrupts) != 0) do_IRQ(regs); #endif @@ -604,6 +635,11 @@ void timer_interrupt(struct pt_regs * regs) calculate_steal_time(); + if (test_perf_event_pending()) { + clear_perf_event_pending(); + perf_event_do_pending(); + } + #ifdef CONFIG_PPC_ISERIES if (firmware_has_feature(FW_FEATURE_ISERIES)) get_lppaca()->int_dword.fields.decr_int = 0;