diff options
author | Oleg Nesterov <oleg@redhat.com> | 2016-07-26 20:57:36 +0200 |
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committer | Ingo Molnar <mingo@kernel.org> | 2016-07-27 11:12:11 +0200 |
commit | ce4f06dcbb5d6d04d202f1b81ac72d5679dcdfc0 (patch) | |
tree | 5f7b351d9cfc0374eeacc3c1034fd7effd5bd9ff /tools/objtool | |
parent | 5cada17426505b09a045cd9e6d7fb6db19b76ea1 (diff) |
stop_machine: Touch_nmi_watchdog() after MULTI_STOP_PREPARE
Suppose that stop_machine(fn) hangs because fn() hangs. In this case NMI
hard-lockup can be triggered on another CPU which does nothing wrong and
the trace from nmi_panic() won't help to investigate the problem.
And this change "fixes" the problem we (seem to) hit in practice.
- stop_two_cpus(0, 1) races with show_state_filter() running on CPU_0.
- CPU_1 already spins in MULTI_STOP_PREPARE state, it detects the soft
lockup and tries to report the problem.
- show_state_filter() enables preemption, CPU_0 calls multi_cpu_stop()
which goes to MULTI_STOP_DISABLE_IRQ state and disables interrupts.
- CPU_1 spends more than 10 seconds trying to flush the log buffer to
the slow serial console.
- NMI interrupt on CPU_0 (which now waits for CPU_1) calls nmi_panic().
Reported-by: Wang Shu <shuwang@redhat.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dave Anderson <anderson@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Link: http://lkml.kernel.org/r/20160726185736.GB4088@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'tools/objtool')
0 files changed, 0 insertions, 0 deletions