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| author | Thomas Gleixner <tglx@linutronix.de> | 2009-06-16 15:33:39 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-06-16 19:47:48 -0700 |
| commit | 8b0b1db0133e4218a9b45c09e53793c039edebe1 (patch) | |
| tree | 551ec8a69652b9856cefcf537bdcfd262f356974 /include/linux/smp.h | |
| parent | 10fc89d01a7ea2ecc2a58d2f4e7700f47178cd62 (diff) | |
| download | linux-8b0b1db0133e4218a9b45c09e53793c039edebe1.tar.gz linux-8b0b1db0133e4218a9b45c09e53793c039edebe1.tar.bz2 linux-8b0b1db0133e4218a9b45c09e53793c039edebe1.zip | |
remove put_cpu_no_resched()
put_cpu_no_resched() is an optimization of put_cpu() which unfortunately
can cause high latencies.
The nfs iostats code uses put_cpu_no_resched() in a code sequence where a
reschedule request caused by an interrupt between the get_cpu() and the
put_cpu_no_resched() can delay the reschedule for at least HZ.
The other users of put_cpu_no_resched() optimize correctly in interrupt
code, but there is no real harm in using the put_cpu() function which is
an alias for preempt_enable(). The extra check of the preemmpt count is
not as critical as the potential source of missing a reschedule.
Debugged in the preempt-rt tree and verified in mainline.
Impact: remove a high latency source
[akpm@linux-foundation.org: build fix]
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: "J. Bruce Fields" <bfields@fieldses.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/smp.h')
| -rw-r--r-- | include/linux/smp.h | 1 |
1 files changed, 0 insertions, 1 deletions
diff --git a/include/linux/smp.h b/include/linux/smp.h index a69db820eed6..9e3d8af09207 100644 --- a/include/linux/smp.h +++ b/include/linux/smp.h @@ -177,7 +177,6 @@ static inline void init_call_single_data(void) #define get_cpu() ({ preempt_disable(); smp_processor_id(); }) #define put_cpu() preempt_enable() -#define put_cpu_no_resched() preempt_enable_no_resched() /* * Callback to arch code if there's nosmp or maxcpus=0 on the |