From b8caed823b39b5a86b694f9ec60a8b43323248e8 Mon Sep 17 00:00:00 2001 From: David Crawshaw Date: Tue, 24 Mar 2015 09:22:35 -0400 Subject: [PATCH] runtime: initialize extra M for cgo during mstart Previously the extra m needed for cgo callbacks was created on the first callback. This works for cgo, however the cgocallback mechanism is also borrowed by badsignal which can run before any cgo calls are made. Now we initialize the extra M at runtime startup before any signal handlers are registered, so badsignal cannot be called until the extra M is ready. Updates #10207. Change-Id: Iddda2c80db6dc52d8b60e2b269670fbaa704c7b3 Reviewed-on: https://go-review.googlesource.com/7978 Reviewed-by: Ian Lance Taylor Run-TryBot: David Crawshaw --- src/runtime/cgocall.go | 5 ----- src/runtime/proc1.go | 5 +++++ src/runtime/sigqueue.go | 9 --------- 3 files changed, 5 insertions(+), 14 deletions(-) diff --git a/src/runtime/cgocall.go b/src/runtime/cgocall.go index e7aeb7bee3e..052830de5ad 100644 --- a/src/runtime/cgocall.go +++ b/src/runtime/cgocall.go @@ -101,11 +101,6 @@ func cgocall_errno(fn, arg unsafe.Pointer) int32 { racereleasemerge(unsafe.Pointer(&racecgosync)) } - // Create an extra M for callbacks on threads not created by Go on first cgo call. - if needextram == 1 && cas(&needextram, 1, 0) { - systemstack(newextram) - } - /* * Lock g to m to ensure we stay on the same stack if we do a * cgo callback. Add entry to defer stack in case of panic. diff --git a/src/runtime/proc1.go b/src/runtime/proc1.go index 0ff3bafbdb8..1c34e4b6917 100644 --- a/src/runtime/proc1.go +++ b/src/runtime/proc1.go @@ -717,6 +717,11 @@ func mstart1() { // Install signal handlers; after minit so that minit can // prepare the thread to be able to handle the signals. if _g_.m == &m0 { + // Create an extra M for callbacks on threads not created by Go. + if needextram == 1 { + needextram = 0 + newextram() + } initsig() } diff --git a/src/runtime/sigqueue.go b/src/runtime/sigqueue.go index df3c9c0e612..9cfe2592db4 100644 --- a/src/runtime/sigqueue.go +++ b/src/runtime/sigqueue.go @@ -165,14 +165,5 @@ func signal_ignore(s uint32) { // This runs on a foreign stack, without an m or a g. No stack split. //go:nosplit func badsignal(sig uintptr) { - // Some external libraries, for example, OpenBLAS, create worker threads in - // a global constructor. If we're doing cpu profiling, and the SIGPROF signal - // comes to one of the foreign threads before we make our first cgo call, the - // call to cgocallback below will bring down the whole process. - // It's better to miss a few SIGPROF signals than to abort in this case. - // See http://golang.org/issue/9456. - if _SIGPROF != 0 && sig == _SIGPROF && needextram != 0 { - return - } cgocallback(unsafe.Pointer(funcPC(sigsend)), noescape(unsafe.Pointer(&sig)), unsafe.Sizeof(sig)) }