diff options
Diffstat (limited to 'libgo/go/runtime/sigqueue.go')
| -rw-r--r-- | libgo/go/runtime/sigqueue.go | 48 |
1 files changed, 11 insertions, 37 deletions
diff --git a/libgo/go/runtime/sigqueue.go b/libgo/go/runtime/sigqueue.go index da2491d15f8..49754f57643 100644 --- a/libgo/go/runtime/sigqueue.go +++ b/libgo/go/runtime/sigqueue.go @@ -11,18 +11,18 @@ // // sigsend is called by the signal handler to queue a new signal. // signal_recv is called by the Go program to receive a newly queued signal. +// // Synchronization between sigsend and signal_recv is based on the sig.state -// variable. It can be in 4 states: sigIdle, sigReceiving, sigSending and sigFixup. -// sigReceiving means that signal_recv is blocked on sig.Note and there are no -// new pending signals. -// sigSending means that sig.mask *may* contain new pending signals, -// signal_recv can't be blocked in this state. -// sigIdle means that there are no new pending signals and signal_recv is not blocked. -// sigFixup is a transient state that can only exist as a short -// transition from sigReceiving and then on to sigIdle: it is -// used to ensure the AllThreadsSyscall()'s mDoFixup() operation -// occurs on the sleeping m, waiting to receive a signal. +// variable. It can be in three states: +// * sigReceiving means that signal_recv is blocked on sig.Note and there are +// no new pending signals. +// * sigSending means that sig.mask *may* contain new pending signals, +// signal_recv can't be blocked in this state. +// * sigIdle means that there are no new pending signals and signal_recv is not +// blocked. +// // Transitions between states are done atomically with CAS. +// // When signal_recv is unblocked, it resets sig.Note and rechecks sig.mask. // If several sigsends and signal_recv execute concurrently, it can lead to // unnecessary rechecks of sig.mask, but it cannot lead to missed signals @@ -63,7 +63,6 @@ const ( sigIdle = iota sigReceiving sigSending - sigFixup ) // sigsend delivers a signal from sighandler to the internal signal delivery queue. @@ -117,9 +116,6 @@ Send: notewakeup(&sig.note) break Send } - case sigFixup: - // nothing to do - we need to wait for sigIdle. - mDoFixupAndOSYield() } } @@ -127,19 +123,6 @@ Send: return true } -// sigRecvPrepareForFixup is used to temporarily wake up the -// signal_recv() running thread while it is blocked waiting for the -// arrival of a signal. If it causes the thread to wake up, the -// sig.state travels through this sequence: sigReceiving -> sigFixup -// -> sigIdle -> sigReceiving and resumes. (This is only called while -// GC is disabled.) -//go:nosplit -func sigRecvPrepareForFixup() { - if atomic.Cas(&sig.state, sigReceiving, sigFixup) { - notewakeup(&sig.note) - } -} - // Called to receive the next queued signal. // Must only be called from a single goroutine at a time. //go:linkname signal_recv os_1signal.signal__recv @@ -167,16 +150,7 @@ func signal_recv() uint32 { } notetsleepg(&sig.note, -1) noteclear(&sig.note) - if !atomic.Cas(&sig.state, sigFixup, sigIdle) { - break Receive - } - // Getting here, the code will - // loop around again to sleep - // in state sigReceiving. This - // path is taken when - // sigRecvPrepareForFixup() - // has been called by another - // thread. + break Receive } case sigSending: if atomic.Cas(&sig.state, sigSending, sigIdle) { |