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| author | Fernando Luis Vázquez Cao <fernando@oss.ntt.co.jp> | 2011-12-13 11:51:53 +0900 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2011-12-14 09:32:05 +0100 |
| commit | 346b46be5f10e4d247160ea94ac34450be60ce1e (patch) | |
| tree | e7515a97d2f0da032c8e1d1371aa94e866c50065 /arch/x86/include/asm/apic.h | |
| parent | b95a7bd700466c10fda84acbd33f70cf66ec91ce (diff) | |
| download | linux-346b46be5f10e4d247160ea94ac34450be60ce1e.tar.gz linux-346b46be5f10e4d247160ea94ac34450be60ce1e.tar.bz2 linux-346b46be5f10e4d247160ea94ac34450be60ce1e.zip | |
x86: Add per-cpu stat counter for APIC ICR read tries
In the IPI delivery slow path (NMI delivery) we retry the ICR
read to check for delivery completion a limited number of times.
[ The reason for the limited retries is that some of the places
where it is used (cpu boot, kdump, etc) IPI delivery might not
succeed (due to a firmware bug or system crash, for example)
and in such a case it is better to give up and resume
execution of other code. ]
This patch adds a new entry to /proc/interrupts, RTR, which
tells user space the number of times we retried the ICR read in
the IPI delivery slow path.
This should give some insight into how well the APIC
message delivery hardware is working - if the counts are way
too large then we are hitting a (very-) slow path way too
often.
Signed-off-by: Fernando Luis Vazquez Cao <fernando@oss.ntt.co.jp>
Cc: Jörn Engel <joern@logfs.org>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Link: http://lkml.kernel.org/n/tip-vzsp20lo2xdzh5f70g0eis2s@git.kernel.org
[ extended the changelog ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/x86/include/asm/apic.h')
| -rw-r--r-- | arch/x86/include/asm/apic.h | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h index 1a6c09af048f..5fe0bd574756 100644 --- a/arch/x86/include/asm/apic.h +++ b/arch/x86/include/asm/apic.h @@ -410,6 +410,9 @@ extern int wakeup_secondary_cpu_via_nmi(int apicid, unsigned long start_eip); #endif #ifdef CONFIG_X86_LOCAL_APIC + +DECLARE_PER_CPU(unsigned, icr_read_retry_count); + static inline u32 apic_read(u32 reg) { return apic->read(reg); |