diff options
Diffstat (limited to 'src/runtime/proc.go')
| -rw-r--r-- | src/runtime/proc.go | 29 |
1 files changed, 10 insertions, 19 deletions
diff --git a/src/runtime/proc.go b/src/runtime/proc.go index 25d39d9ba3..8d5f2fc793 100644 --- a/src/runtime/proc.go +++ b/src/runtime/proc.go @@ -1372,6 +1372,9 @@ func casGToWaiting(gp *g, old uint32, reason waitReason) { // casGToWaitingForSuspendG transitions gp from old to _Gwaiting, and sets the wait reason. // The wait reason must be a valid isWaitingForSuspendG wait reason. // +// While a goroutine is in this state, it's stack is effectively pinned. +// The garbage collector must not shrink or otherwise mutate the goroutine's stack. +// // Use this over casgstatus when possible to ensure that a waitreason is set. func casGToWaitingForSuspendG(gp *g, old uint32, reason waitReason) { if !reason.isWaitingForSuspendG() { @@ -1608,18 +1611,11 @@ func stopTheWorldWithSema(reason stwReason) worldStop { // stack 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, now that we switched to _Gwaiting, specifically if we're - // doing this during the mark phase (mark termination excepted, since - // we know that stack scanning is done by that point). 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. + // casGToWaitingForSuspendG marks the goroutine as ineligible for a + // stack shrink, effectively pinning the stack in memory for the duration. // // N.B. The execution tracer is not aware of this status transition and - // andles it specially based on the wait reason. + // handles it specially based on the wait reason. casGToWaitingForSuspendG(getg().m.curg, _Grunning, waitReasonStoppingTheWorld) trace := traceAcquire() @@ -2106,16 +2102,11 @@ func forEachP(reason waitReason, fn func(*p)) { // deadlock as we attempt to preempt a goroutine that's trying // to preempt us (e.g. for a stack scan). // - // 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. + // casGToWaitingForSuspendG marks the goroutine as ineligible for a + // stack shrink, effectively pinning the stack in memory for the duration. // - // N.B. The execution tracer is not aware of this status - // transition and handles it specially based on the - // wait reason. + // N.B. The execution tracer is not aware of this status transition and + // handles it specially based on the wait reason. casGToWaitingForSuspendG(gp, _Grunning, reason) forEachPInternal(fn) casgstatus(gp, _Gwaiting, _Grunning) |