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syscall: syscall.AllThreadsSyscall signal handling fixes

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The runtime support for syscall.AllThreadsSyscall() functions had
some corner case deadlock issues when signal handling was in use.
This was observed in at least 3 build test failures on ppc64 and
amd64 architecture CGO_ENABLED=0 builds over the last few months.

The fixes involve more controlled handling of signals while the
AllThreads mechanism is being executed. Further details are
discussed in bug #44193.

The all-threads syscall support is new in go1.16, so earlier
releases are not affected by this bug.

Fixes #44193

Change-Id: I01ba8508a6e1bb2d872751f50da86dd07911a41d
Reviewed-on: https://go-review.googlesource.com/c/go/+/305149
Reviewed-by: Michael Pratt <mpratt@google.com>
Trust: Michael Pratt <mpratt@google.com>
Trust: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Michael Pratt <mpratt@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
This commit is contained in:
Andrew G. Morgan 2021-03-26 19:27:22 -07:00 • committed by Michael Pratt
parent 54af9fd9e6
commit 7e97e4e8cc
4 changed files with 96 additions and 7 deletions
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7
src/runtime/runtime2.go
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@ -554,10 +554,13 @@ type m struct {
syscalltick uint32
freelink *m // on sched.freem
// mFixup is used to synchronize OS related m state (credentials etc)
// use mutex to access.
// mFixup is used to synchronize OS related m state
// (credentials etc) use mutex to access. To avoid deadlocks
// an atomic.Load() of used being zero in mDoFixupFn()
// guarantees fn is nil.
mFixup struct {
lock mutex
used uint32
fn func(bool) bool
}