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console_linux: Fix race: lock Cond before Signal. #27

Merged
merged 1 commit into from
Jul 5, 2018
Merged

console_linux: Fix race: lock Cond before Signal. #27

merged 1 commit into from
Jul 5, 2018

Commits on Jul 3, 2018

  1. console_linux: Fix race: lock Cond before Signal. 

    Possible race:

Thread1:			Thread2:
line 178: Read() -> EAGAIN	...
<reschedule>			line 110: EpollWait()
...				line 124: signalRead()
...				...
line 191: Wait()		...
				line 110: EpollWait()

Thread2 (epoll) sends signalRead() (via sync.Cond) but Thread1 is not waiting
yet. Then it starts to wait, but no more signals will arrive (because Thread2
is sleeping in EpollWait() on edge-triggered epoll.

To prevent this race one should held Lock when sending signalRead().

The same situation goes with Write loop.

Bug was reported to docker: docker/for-linux#353

Signed-off-by: Alexander Gerasiov <gerasiov@yandex-team.ru>
    @gerasiov
    gerasiov committed Jul 3, 2018
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