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| author | Cherry Zhang <cherryyz@google.com> | 2020-03-16 20:08:00 -0400 |
|---|---|---|
| committer | Carlos Amedee <carlos@golang.org> | 2020-03-18 18:38:30 +0000 |
| commit | e577ba98d8d9f4464d6dfaaf2fa51d328233c81e (patch) | |
| tree | 019caafc845254edee73864783d85779f649e1c1 | |
| parent | 229247d33b717ce7729e43a8fde3a095e376cf3d (diff) | |
| download | go-e577ba98d8d9f4464d6dfaaf2fa51d328233c81e.tar.gz go-e577ba98d8d9f4464d6dfaaf2fa51d328233c81e.zip | |
[release-branch.go1.14] runtime: don't send preemption signal if there is a signal pending
If multiple threads call preemptone to preempt the same M, it may
send many signals to the same M such that it hardly make
progress, causing live-lock problem. Only send a signal if there
isn't already one pending.
Updates #37741.
Fixes #37833.
Change-Id: Id94adb0b95acbd18b23abe637a8dcd81ab41b452
Reviewed-on: https://go-review.googlesource.com/c/go/+/223737
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
(cherry picked from commit 0c0e8f224d5724e317952f77d215a752a3a7b7d9)
Reviewed-on: https://go-review.googlesource.com/c/go/+/223939
Reviewed-by: Austin Clements <austin@google.com>
| -rw-r--r-- | src/runtime/runtime2.go | 4 | ||||
| -rw-r--r-- | src/runtime/signal_unix.go | 10 |
2 files changed, 13 insertions, 1 deletions
diff --git a/src/runtime/runtime2.go b/src/runtime/runtime2.go index 99eb19eb0c..2a872bfba9 100644 --- a/src/runtime/runtime2.go +++ b/src/runtime/runtime2.go @@ -540,6 +540,10 @@ type m struct { // requested, but fails. Accessed atomically. preemptGen uint32 + // Whether this is a pending preemption signal on this M. + // Accessed atomically. + signalPending uint32 + dlogPerM mOS diff --git a/src/runtime/signal_unix.go b/src/runtime/signal_unix.go index d2e6693805..f18e6b5785 100644 --- a/src/runtime/signal_unix.go +++ b/src/runtime/signal_unix.go @@ -333,6 +333,7 @@ func doSigPreempt(gp *g, ctxt *sigctxt) { // Acknowledge the preemption. atomic.Xadd(&gp.m.preemptGen, 1) + atomic.Store(&gp.m.signalPending, 0) } const preemptMSupported = pushCallSupported @@ -359,7 +360,14 @@ func preemptM(mp *m) { // required). return } - signalM(mp, sigPreempt) + if atomic.Cas(&mp.signalPending, 0, 1) { + // If multiple threads are preempting the same M, it may send many + // signals to the same M such that it hardly make progress, causing + // live-lock problem. Apparently this could happen on darwin. See + // issue #37741. + // Only send a signal if there isn't already one pending. + signalM(mp, sigPreempt) + } } // sigFetchG fetches the value of G safely when running in a signal handler. |