diff options
Diffstat (limited to 'src/runtime/proc.go')
| -rw-r--r-- | src/runtime/proc.go | 44 |
1 files changed, 40 insertions, 4 deletions
diff --git a/src/runtime/proc.go b/src/runtime/proc.go index 72e6f0da0c..c06697ef6d 100644 --- a/src/runtime/proc.go +++ b/src/runtime/proc.go @@ -962,8 +962,23 @@ func restartg(gp *g) { // goroutines. func stopTheWorld(reason string) { semacquire(&worldsema) - getg().m.preemptoff = reason - systemstack(stopTheWorldWithSema) + gp := getg() + gp.m.preemptoff = reason + systemstack(func() { + // Mark the goroutine which called stopTheWorld preemptible so its + // stack may be scanned. + // This lets a mark worker scan us while we try to stop the world + // since otherwise we could get in a mutual preemption deadlock. + // We must not modify anything on the G stack because a stack shrink + // may occur. A stack shrink is otherwise OK though because in order + // to return from this function (and to leave the system stack) we + // must have preempted all goroutines, including any attempting + // to scan our stack, in which case, any stack shrinking will + // have already completed by the time we exit. + casgstatus(gp, _Grunning, _Gwaiting) + stopTheWorldWithSema() + casgstatus(gp, _Gwaiting, _Grunning) + }) } // startTheWorld undoes the effects of stopTheWorld. @@ -975,10 +990,31 @@ func startTheWorld() { getg().m.preemptoff = "" } -// Holding worldsema grants an M the right to try to stop the world -// and prevents gomaxprocs from changing concurrently. +// stopTheWorldGC has the same effect as stopTheWorld, but blocks +// until the GC is not running. It also blocks a GC from starting +// until startTheWorldGC is called. +func stopTheWorldGC(reason string) { + semacquire(&gcsema) + stopTheWorld(reason) +} + +// startTheWorldGC undoes the effects of stopTheWorldGC. +func startTheWorldGC() { + startTheWorld() + semrelease(&gcsema) +} + +// Holding worldsema grants an M the right to try to stop the world. var worldsema uint32 = 1 +// Holding gcsema grants the M the right to block a GC, and blocks +// until the current GC is done. In particular, it prevents gomaxprocs +// from changing concurrently. +// +// TODO(mknyszek): Once gomaxprocs and the execution tracer can handle +// being changed/enabled during a GC, remove this. +var gcsema uint32 = 1 + // stopTheWorldWithSema is the core implementation of stopTheWorld. // The caller is responsible for acquiring worldsema and disabling // preemption first and then should stopTheWorldWithSema on the system |