[Bug uprobes/6841] system-wide utrace syscall tracing script don't respond signal

[mhiramat at redhat dot com]

------- Additional Comments From mhiramat at redhat dot com  2008-08-17 20:22 -------
After deep investigation by stap, I found a strange behaviour of utrace.
At utrace_set_flags(), it calls quiesce() and set TIF_SIGPENDING flag to target 
thread, but utrace doesn't wake it up. If the target is waiting signal at that
time(ex. sigwait), it fails to wakeup when a signal was sent because it already
has TIF_SIGPENDING (see __group_complete_signal() and wants_signal() in
kernel/signal.c).

I think utrace_set_flags()/quiesce() should not use TIF_SIGPENDING.


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http://sourceware.org/bugzilla/show_bug.cgi?id=6841

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