runtime: make it harder to introduce deadlocks with forEachP

[gostls13.git] / src / runtime / mgc.go

diff --git a/src/runtime/mgc.go b/src/runtime/mgc.go
index 30d2f1d3852b4430c6ac2039e5a0f3d1dcf43ba3..d015d6dbabaa8035f28b5debad991c9da3840195 100644 (file)
--- a/src/runtime/mgc.go
+++ b/src/runtime/mgc.go
@@ -824,31 +824,22 @@ top:
 
        // Flush all local buffers and collect flushedWork flags.
        gcMarkDoneFlushed = 0
-       systemstack(func() {
-               gp := getg().m.curg
-               // Mark the user stack as preemptible so that it may be scanned.
-               // Otherwise, our attempt to force all P's to a safepoint could
-               // result in a deadlock as we attempt to preempt a worker that's
-               // trying to preempt us (e.g. for a stack scan).
-               casGToWaiting(gp, _Grunning, waitReasonGCMarkTermination)
-               forEachP(func(pp *p) {
-                       // Flush the write barrier buffer, since this may add
-                       // work to the gcWork.
-                       wbBufFlush1(pp)
-
-                       // Flush the gcWork, since this may create global work
-                       // and set the flushedWork flag.
-                       //
-                       // TODO(austin): Break up these workbufs to
-                       // better distribute work.
-                       pp.gcw.dispose()
-                       // Collect the flushedWork flag.
-                       if pp.gcw.flushedWork {
-                               atomic.Xadd(&gcMarkDoneFlushed, 1)
-                               pp.gcw.flushedWork = false
-                       }
-               })
-               casgstatus(gp, _Gwaiting, _Grunning)
+       forEachP(waitReasonGCMarkTermination, func(pp *p) {
+               // Flush the write barrier buffer, since this may add
+               // work to the gcWork.
+               wbBufFlush1(pp)
+
+               // Flush the gcWork, since this may create global work
+               // and set the flushedWork flag.
+               //
+               // TODO(austin): Break up these workbufs to
+               // better distribute work.
+               pp.gcw.dispose()
+               // Collect the flushedWork flag.
+               if pp.gcw.flushedWork {
+                       atomic.Xadd(&gcMarkDoneFlushed, 1)
+                       pp.gcw.flushedWork = false
+               }
        })
 
        if gcMarkDoneFlushed != 0 {
@@ -1116,18 +1107,16 @@ func gcMarkTermination() {
        //
        // Also, flush the pinner cache, to avoid leaking that memory
        // indefinitely.
-       systemstack(func() {
-               forEachP(func(pp *p) {
-                       pp.mcache.prepareForSweep()
-                       if pp.status == _Pidle {
-                               systemstack(func() {
-                                       lock(&mheap_.lock)
-                                       pp.pcache.flush(&mheap_.pages)
-                                       unlock(&mheap_.lock)
-                               })
-                       }
-                       pp.pinnerCache = nil
-               })
+       forEachP(waitReasonFlushProcCaches, func(pp *p) {
+               pp.mcache.prepareForSweep()
+               if pp.status == _Pidle {
+                       systemstack(func() {
+                               lock(&mheap_.lock)
+                               pp.pcache.flush(&mheap_.pages)
+                               unlock(&mheap_.lock)
+                       })
+               }
+               pp.pinnerCache = nil
        })
        if sl.valid {
                // Now that we've swept stale spans in mcaches, they don't