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Message-ID: <20100414064603.GA4714@drongo>
Date: Wed, 14 Apr 2010 16:46:04 +1000
From: Paul Mackerras <paulus@...ba.org>
To: Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Ingo Molnar <mingo@...e.hu>,
Peter Zijlstra <peterz@...radead.org>
Cc: linux-kernel@...r.kernel.org, linuxppc-dev@...abs.org,
Anton Blanchard <anton@...ba.org>
Subject: [PATCH] powerpc/perf_event: Fix oops due to perf_event_do_pending
call
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 <paulus@...ba.org>
Cc: stable@...nel.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 <linux/bootmem.h>
#include <linux/pci.h>
#include <linux/debugfs.h>
-#include <linux/perf_event.h>
#include <asm/uaccess.h>
#include <asm/system.h>
@@ -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;
--
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