Messages in this thread | | | Date | Wed, 6 Apr 2016 21:51:33 +0200 | From | Heiko Carstens <> | Subject | Re: [PATCH] cpu/hotplug: fix rollback during error-out in __cpu_disable() |
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On Tue, Apr 05, 2016 at 05:59:04PM +0200, Sebastian Andrzej Siewior wrote: > If we error out in __cpu_disable() (via takedown_cpu() which is > currently the last one that can fail) we don't rollback entirely to > CPUHP_ONLINE (where we started) but to CPUHP_AP_ONLINE_IDLE. This > happens because the former states were on the target CPU (the AP states) > and during the rollback we go back until the first BP state we started. > During the next cpu_down attempt (on the same failed CPU) will take > forever because the cpuhp thread is still down. > > The fix this I rollback to where we started in _cpu_down() via a workqueue > to ensure that those callback will be run on the target CPU in > non-atomic context (as in normal cpu_up()). > The workqueues should be working again because the CPU_DOWN_FAILED were > already invoked. > > notify_online() has been marked as ->skip_onerr because otherwise we > will see the CPU_ONLINE notifier in addition to the CPU_DOWN_FAILED. > However with ->skip_onerr we neither see CPU_ONLINE nor CPU_DOWN_FAILED > if something in between (CPU_DOWN_FAILED … CPUHP_TEARDOWN_CPU). > Currently there is nothing. > > This regression got probably introduce in the rework while we introduced > the hotplug thread to offload the work to the target CPU. > > Fixes: 4cb28ced23c4 ("cpu/hotplug: Create hotplug threads") > Reported-by: Heiko Carstens <heiko.carstens@de.ibm.com> > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> > --- > kernel/cpu.c | 19 +++++++++++++++++++ > 1 file changed, 19 insertions(+)
This fixes the issue that a second cpu_down() will take forever, if __cpu_disable() fails.
However it does not fix the issue that CPU_DOWN_FAILED will be seen on a different cpu than the cpu that was supposed to be taken offline.
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