Re: PID-reuse races fix, introduced GCC validation brakage

[Yvan Roux]

On 30 March 2016 at 17:18, Christophe Lyon <address@hidden> wrote:
> On 30 March 2016 at 17:03, Yvan Roux <address@hidden> wrote:
>> Hi,
>>
>> https://lists.gnu.org/archive/html/dejagnu/2015-07/msg00000.html
>>
>> this patch introduced  a new failure related to GDB testing, but this
>> time in GCC guality part of the testsuite.  When
>> gcc/testsuite/gcc.dg/guality/example.c is executed we have this set of
>> processes started
>>
>> PID  PPID     command
>> 100  99          ./example.exe
>> 101  99          cat
>> 102  100        sh -c gdb -nx -nw --quiet > /dev/null 2>&1 ./example.exe
>> 103  102        gdb -nx -nw --quiet ./example.exe
>>
>> The issue is that when close_wait_program is called pid="100 101" and
>> when the "wait" returns none of these 4 processes is actually killed,
>> and the killing of the "kill pipeline" made these pids untouched and
>> the validation hangs forever.
>>
>
> It seems to me that close_wait_program assumes that pid is a number,
> while it can be list.
>
> Or am I mistaken?

yes, that's it, only the first element of the pid list gets the "-"
for the group pid for instance, but it has no real impact, at least on
the cases I looked at.  My on-going fix cleans that as well.

>> I not sure what's the best way to fix this issue without
>> re-introducing the pid race in GDB.  I'm testing a solution which
>> first gather all the childs processes of the close_wait_program pid
>> input (with a recursive call of pgrep -P) and then kill them all with
>> a -15, my assumption is that killing explicitly all the processes
>> (maybe in the child -> parent order) will avoid the need of stdin
>> closing and the pid re-use race, but I might be wrong, and all
>> comments are welcome.  It works so far on a subset of the testsuite,
>> but I'm still validating this approach.  Now, maybe just the reducing
>> the sleeping time might workaround the issue....
>>
>> Cheers,
>> Yvan
>>
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