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powerpc/perf_event: Fix oops due to perf_event_do_pending call

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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@samba.org>
Cc: stable@kernel.org
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Paul Mackerras 2010-04-13 20:46:04 +00:00 committed by Benjamin Herrenschmidt
parent cea0d767c2
commit 0fe1ac48be
5 changed files with 48 additions and 66 deletions
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38
arch/powerpc/include/asm/hw_irq.h
View file

@ -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 */

1
arch/powerpc/kernel/asm-offsets.c
View file

@ -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,

9
arch/powerpc/kernel/entry_64.S
View file

@ -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 */

6
arch/powerpc/kernel/irq.c
View file

@ -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

60
arch/powerpc/kernel/time.c
View file

@ -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;