[RFC] Probes don't hit in an already running process

[David Smith]

On 03/07/2014 04:27 PM, Torsten Polle wrote:
> Hi,
> 
> I've made the observation that probes sometimes don't hit when I start
> staprun after the process (where the probes should hit) started.  After
> some tests, I found out that only multi-thread processes were affected
> under a certain condition.
> 
> The patch below fixes the issue for me. But I've no clue about possible
> side effects. In my first attempt to fix the issue, I also included the
> calls to __stp_call_callbacks() into the guarded area. My probes hit,
> but calls to usymname(uaddr()) in the probe body only printed the
> address instead of the symbol of the probed function.
> 
> Any advice of how I can improve the patch is appreciated.

Hmm. we've had this problem before, and I thought we fixed it. See
PR12642 (utrace: taskfinder misses events when main thread does not go
through at least one quiesce):

<https://sourceware.org/bugzilla/show_bug.cgi?id=12642>

One of the things the commit that fixes that bug does is add a test
case, called 'main_quiesce.exp'. Does that pass or fail for you (run
"make installcheck RUNTESTFLAGS=main_quiesce.exp")? If it passes, we
need to figure out what is different about your multi-thread process
that still causes this to happen.

-- 
David Smith
dsmith@redhat.com
Red Hat
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