[lttng-dev] Ping: Re: [PATCH lttng-ust] Bugfix for http://bugs.lttng.org/issues/745

[Mathieu Desnoyers]

----- Original Message -----
> From: "Paul Woegerer" <Paul_Woegerer at mentor.com>
> To: lttng-dev at lists.lttng.org, "mathieu desnoyers" <mathieu.desnoyers at efficios.com>
> Sent: Thursday, July 10, 2014 8:49:37 AM
> Subject: Ping: Re: [PATCH lttng-ust] Bugfix for http://bugs.lttng.org/issues/745
> 
> Hi Mathieu,
> 
> Since we have no other options currently (see LD_AUDIT discussion) we
> really should get this merged into master. As said, it's thoroughly
> tested and should not cause any ill side-effects.

Hi Paul,

Sorry about the delayed answer, I was busy implementing a tool that extracts
UST buffers in the event of a system crash.

Looking at your patch below, I wonder why you use a semaphore (0, 1) rather
than a mutex ? I guess you could achieve the same result with a pthread
mutex ? If so, it would be better, because it makes it easier to understand
mutex nesting.

Thanks,

Mathieu

> 
> Many Thanks,
> Paul
> 
> On 07/04/2014 02:21 PM, Paul Woegerer wrote:
> > Since (at least) in the short term LD_AUDIT will not be able to make
> > sem_wait()
> > in the static constructor go away I provide the following patch to fix
> > http://bugs.lttng.org/issues/745.
> > 
> > It works by making the process of forking mutual exclusive with base
> > address
> > statedumping that happens from the ust_listener_thread.
> > 
> > I have tested this fix with several variations of (constrained) fork bombs
> > (including tests/regression/ust/daemon from lttng-tools) on x86_64,
> > ARM(imx6q)
> > and powerpc(P4080DS). It works reliable. I could not find any issues with
> > this
> > approach.
> > 
> > Paul Woegerer (1):
> >   Bugfix for #745 deadlock with baddr statedump+fork
> > 
> >  liblttng-ust/lttng-ust-comm.c | 21 +++++++++++++++++++++
> >  1 file changed, 21 insertions(+)
> > 
> 
> 
> --
> Paul Woegerer, SW Development Engineer
> Sourcery Analyzer <http://go.mentor.com/sourceryanalyzer>
> Mentor Graphics, Embedded Software Division
> 

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com