Re: [PATCH] malloc: Re-add protection for recursive calls to __malloc_fork_lock_parent

["Tulio Magno Quites Machado Filho" <tuliom at linux dot vnet dot ibm dot com>]

Florian Weimer <fweimer@redhat.com> writes:

> On 05/11/2016 12:33 AM, Tulio Magno Quites Machado Filho wrote:
>>
>> I wonder if it requires a new bug report as 8a727af9 has been backported
>> to glibc 2.23.
>
> We already have a bug for this, I think:
>
>    https://sourceware.org/bugzilla/show_bug.cgi?id=19703

Thanks for pointing that.

> I've just attached a more reliable test case to this bug.  For me, it is 
> quite reliable with even quite old glibcsâthe test case indicates 
> delivery of a few signals and then goes into deadlock.
>
> I believe the new test is completely valid because sigusr1_handler calls 
> only async-signal-safe functions (the old one should really call _exit 
> instead of exit in the signal handler).
>
> I tried this test with current master and your patch applied on top, and 
> I still get deadlocks.  Can you give this test a try as well?

It did get into deadlock soon here.

> A true fix for bug 19703 depends on bug 19702 (Provide a flag indicating 
> whether a thread is in a signal handler), which is not easy to address 
> because we need an async-signal-safe sigaction/signal function and need 
> to atomically change the signal handler and its associated flags.

Thanks for pointing that too!

-- 
Tulio Magno