[asterisk-dev] [Code Review] 2824: Fix DEBUG_THREADS when lock is acquired in __constructor__

[Mark Michelson]

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Ship it!



/branches/1.8/main/utils.c
<https://reviewboard.asterisk.org/r/2824/#comment18789>

    s/as/has/


- Mark Michelson


On Sept. 5, 2013, 9:39 p.m., David Lee wrote:
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> https://reviewboard.asterisk.org/r/2824/
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> 
> (Updated Sept. 5, 2013, 9:39 p.m.)
> 
> 
> Review request for Asterisk Developers, Matt Jordan and Mark Michelson.
> 
> 
> Bugs: ASTERISK-22455
>     https://issues.asterisk.org/jira/browse/ASTERISK-22455
> 
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> Repository: Asterisk
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> Description
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> 
> This patch fixes some long-standing bugs in debug threads that were
> exacerbated with recent Optional API work in Asterisk 12.
> 
> With debug threads enabled, on some systems, there's a lock ordering
> problem between our mutex and glibc's mutex protecting its module list
> (Ubuntu Lucid, glibc 2.11.1 in this instance). In one thread, the module
> list will be locked before acquiring our mutex. In another thread, our
> mutex will be locked before locking the module list (which happens in
> the depths of calling backtrace()).
> 
> This patch fixes this issue by moving backtrace() calls outside of
> critical sections that have the mutex acquired. The bigger change was to
> reentrancy tracking for ast_cond_{timed,}wait, which wrongly assumed
> that waiting on the mutex was equivalent to a single unlock (it actually
> suspends all recursive locks on the mutex).
> 
> 
> Diffs
> -----
> 
>   /branches/1.8/main/utils.c 398497 
>   /branches/1.8/main/lock.c 398497 
>   /branches/1.8/include/asterisk/lock.h 398497 
> 
> Diff: https://reviewboard.asterisk.org/r/2824/diff/
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> 
> Testing
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> Asterisk 12, DEBUG_THREADS+OPTIONAL_API on Ubuntu Lucid starts without
> deadlock.
> 
> Asterisk 1.8, DEBUG_THREADS runs fine.
> 
> 
> Thanks,
> 
> David Lee
> 
>

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