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runtime: record current PC for SIGPROF on non-Go thread

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If we get a SIGPROF on a non-Go thread, and the program has not called
runtime.SetCgoTraceback so we have no way to collect a stack trace, then
record a profile that is just the PC where the signal occurred. That
will at least point the user to the right area.

Retrieving the PC from the sigctxt in a signal handler on a non-G thread
required marking a number of trivial sigctxt methods as nosplit, and,
for extra safety, nowritebarrierrec.

The test shows that the existing test CgoPprofThread test does not test
the stack trace, just the profile signal. Leaving that for later.

Change-Id: I8f8f3ff09ac099fc9d9df94b5a9d210ffc20c4ab
Reviewed-on: https://go-review.googlesource.com/30252
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
This commit is contained in:
Ian Lance Taylor 2016-10-04 07:11:55 -07:00
parent c24cc40075
commit d03e8b226c
38 changed files with 726 additions and 491 deletions
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9
src/runtime/signal_unix.go
View file

@ -202,15 +202,12 @@ func sigtrampgo(sig uint32, info *siginfo, ctx unsafe.Pointer) {
}
g := getg()
if g == nil {
c := &sigctxt{info, ctx}
if sig == _SIGPROF {
// Ignore profiling signals that arrive on
// non-Go threads. On some systems they will
// be handled directly by the signal handler,
// by calling sigprofNonGo, in which case we won't
// get here anyhow.
sigprofNonGoPC(c.sigpc())
return
}
badsignal(uintptr(sig), &sigctxt{info, ctx})
badsignal(uintptr(sig), c)
return
}