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author | Thomas Gleixner <tglx@linutronix.de> | 2007-05-23 13:58:18 -0700 |
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committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-05-23 20:14:15 -0700 |
commit | 98d8256739f2c6c636fa2da359f5949c739ae839 (patch) | |
tree | e2f92238779ff3012b47a8dd93d57b86b6949793 /Documentation/firmware_class | |
parent | 40acc095302aee380491df5f58d98945243468ec (diff) |
Prevent going idle with softirq pending
The NOHZ patch contains a check for softirqs pending when a CPU goes idle.
The BUG is unrelated to NOHZ, it just was made visible by the NOHZ patch.
The BUG showed up mainly on P4 / hyperthreading enabled machines which lead
the investigations into the wrong direction in the first place. The real
cause is in cond_resched_softirq():
cond_resched_softirq() is enabling softirqs without invoking the softirq
daemon when softirqs are pending. This leads to the warning message in the
NOHZ idle code:
t1 runs softirq disabled code on CPU#0
interrupt happens, softirq is raised, but deferred (softirqs disabled)
t1 calls cond_resched_softirq()
enables softirqs via _local_bh_enable()
calls schedule()
t2 runs
t1 is migrated to CPU#1
t2 is done and invokes idle()
NOHZ detects the pending softirq
Fix: change _local_bh_enable() to local_bh_enable() so the softirq
daemon is invoked.
Thanks to Anant Nitya for debugging this with great patience !
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/firmware_class')
0 files changed, 0 insertions, 0 deletions