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powerpc: Provide a way to defer perf counter work until interrupts are enabled

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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 <paulus@samba.org>
This commit is contained in:
Paul Mackerras
2009-01-09 16:52:19 +11:00
parent d662ed2673
commit 93a6d3ce69
5 changed files with 52 additions and 0 deletions
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1
arch/powerpc/kernel/asm-offsets.c
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@@ -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));