[ltt-dev] [UST PATCH] Fix the once in a while freeze of the tests

Yannick Brosseau yannick.brosseau at gmail.com
Sun Feb 20 10:45:09 EST 2011

On 2011-02-20 10:17, Mathieu Desnoyers wrote:
> * Mathieu Desnoyers (compudj at krystal.dyndns.org) wrote:
>> * Yannick Brosseau (yannick.brosseau at gmail.com) wrote:
>>> Sometimes, the thread in the read function would lock the pipe so the
>>> setlinebuf would freeze on it. Set the linebuf before we create the
>>> thread to fix this deadlock
>> Can you update the description to show which locks are involved in this
>> deadlock scenario ? E.g.
>> - CPU A               - CPU B
>> function              function
>> lock A (taken)        lock B (taken)
>> lock B (waiting)
>>                       lock A (waiting)  <-- deadlock
>> Or show it with the lock chain dependency analysis. But it's important
>> to have this information along with this kind of fix.
> Hrm, ok I looked at tap.c, and it's not a deadlock at all: it's rather
> that the _tap_comment_stdout thread can start using pipe_r_file when it
> is still uninitialized.
I found a lock in the calls to fgets and setlinebuf, deep in the glibc.
If what you says is true, the fix I've proposed is not right. Its the
pthread_create that should be moved.

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