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author | Andrew G. Morgan <agm@google.com> | 2020-11-12 21:19:52 -0800 |
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committer | Ian Lance Taylor <iant@golang.org> | 2020-12-23 02:10:51 +0000 |
commit | b0b0d9828308368e9fbd59ec5de55801f568f720 (patch) | |
tree | 749e40dadc88de8406fa3617592d9a6ac8c64e00 /src/runtime/signal_unix.go | |
parent | 223331fc0cf5b23fbb9999eb1164b23695ef612a (diff) | |
download | go-b0b0d9828308368e9fbd59ec5de55801f568f720.tar.gz go-b0b0d9828308368e9fbd59ec5de55801f568f720.zip |
runtime: linux iscgo support for not blocking nptl signals
Under linux+cgo, OS threads are launched via pthread_create().
This abstraction, under linux, requires we avoid blocking
signals 32,33 and 34 indefinitely because they are needed to
reliably execute POSIX-semantics threading in glibc and/or musl.
When blocking signals the go runtime generally re-enables them
quickly. However, when a thread exits (under cgo, this is
via a return from mstart()), we avoid a deadlock in C-code by
not blocking these three signals.
Fixes #42494
Change-Id: I02dfb2480a1f97d11679e0c4b132b51bddbe4c14
Reviewed-on: https://go-review.googlesource.com/c/go/+/269799
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
Trust: Tobias Klauser <tobias.klauser@gmail.com>
Diffstat (limited to 'src/runtime/signal_unix.go')
-rw-r--r-- | src/runtime/signal_unix.go | 19 |
1 files changed, 15 insertions, 4 deletions
diff --git a/src/runtime/signal_unix.go b/src/runtime/signal_unix.go index e8f39c3321..382ba37a87 100644 --- a/src/runtime/signal_unix.go +++ b/src/runtime/signal_unix.go @@ -1042,15 +1042,26 @@ func msigrestore(sigmask sigset) { sigprocmask(_SIG_SETMASK, &sigmask, nil) } -// sigblock blocks all signals in the current thread's signal mask. +// sigsetAllExiting is used by sigblock(true) when a thread is +// exiting. sigset_all is defined in OS specific code, and per GOOS +// behavior may override this default for sigsetAllExiting: see +// osinit(). +var sigsetAllExiting = sigset_all + +// sigblock blocks signals in the current thread's signal mask. // This is used to block signals while setting up and tearing down g -// when a non-Go thread calls a Go function. -// The OS-specific code is expected to define sigset_all. +// when a non-Go thread calls a Go function. When a thread is exiting +// we use the sigsetAllExiting value, otherwise the OS specific +// definition of sigset_all is used. // This is nosplit and nowritebarrierrec because it is called by needm // which may be called on a non-Go thread with no g available. //go:nosplit //go:nowritebarrierrec -func sigblock() { +func sigblock(exiting bool) { + if exiting { + sigprocmask(_SIG_SETMASK, &sigsetAllExiting, nil) + return + } sigprocmask(_SIG_SETMASK, &sigset_all, nil) } |