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runtime: wait for preemption signals before syscall.Exec

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Fixes #41702
Fixes #42023

Change-Id: If07f40b1d73b8f276ee28ffb8b7214175e56c24d
Reviewed-on: https://go-review.googlesource.com/c/go/+/262817
Trust: Ian Lance Taylor <iant@golang.org>
Trust: Bryan C. Mills <bcmills@google.com>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
This commit is contained in:
Ian Lance Taylor 2020-10-15 14:39:12 -07:00
parent 3eae1a9058
commit 05739d6f17
2 changed files with 32 additions and 0 deletions
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21
src/runtime/proc.go
View File

@ -1311,6 +1311,14 @@ found:
checkdead()
unlock(&sched.lock)
if GOOS == "darwin" {
// Make sure pendingPreemptSignals is correct when an M exits.
// For #41702.
if atomic.Load(&m.signalPending) != 0 {
atomic.Xadd(&pendingPreemptSignals, -1)
}
}
if osStack {
// Return from mstart and let the system thread
// library free the g0 stack and terminate the thread.
@ -3510,11 +3518,24 @@ func syscall_runtime_AfterForkInChild() {
inForkedChild = false
}
// pendingPreemptSignals is the number of preemption signals
// that have been sent but not received. This is only used on Darwin.
// For #41702.
var pendingPreemptSignals uint32
// Called from syscall package before Exec.
//go:linkname syscall_runtime_BeforeExec syscall.runtime_BeforeExec
func syscall_runtime_BeforeExec() {
// Prevent thread creation during exec.
execLock.lock()
// On Darwin, wait for all pending preemption signals to
// be received. See issue #41702.
if GOOS == "darwin" {
for int32(atomic.Load(&pendingPreemptSignals)) > 0 {
osyield()
}
}
}
// Called from syscall package after Exec.

11
src/runtime/signal_unix.go
View File

@ -335,6 +335,10 @@ func doSigPreempt(gp *g, ctxt *sigctxt) {
// Acknowledge the preemption.
atomic.Xadd(&gp.m.preemptGen, 1)
atomic.Store(&gp.m.signalPending, 0)
if GOOS == "darwin" {
atomic.Xadd(&pendingPreemptSignals, -1)
}
}
const preemptMSupported = true
@ -364,6 +368,10 @@ func preemptM(mp *m) {
}
if atomic.Cas(&mp.signalPending, 0, 1) {
if GOOS == "darwin" {
atomic.Xadd(&pendingPreemptSignals, 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
@ -435,6 +443,9 @@ func sigtrampgo(sig uint32, info *siginfo, ctx unsafe.Pointer) {
// no non-Go signal handler for sigPreempt.
// The default behavior for sigPreempt is to ignore
// the signal, so badsignal will be a no-op anyway.
if GOOS == "darwin" {
atomic.Xadd(&pendingPreemptSignals, -1)
}
return
}
c.fixsigcode(sig)