runtime: fix another race in bgsweep

It's possible that bgsweep constantly does not catch up for some reason,
in this case runfinq was not woken at all.

R=rsc
CC=golang-codereviews
https://golang.org/cl/75940043

diff --git a/src/pkg/runtime/mgc0.c b/src/pkg/runtime/mgc0.c
index b7f6adf3941e06039ba3cbdcfc82b12e8eb023fe..a726fb41d167555ab1745159837f2bb9cfb32d92 100644 (file)
--- a/src/pkg/runtime/mgc0.c
+++ b/src/pkg/runtime/mgc0.c
@@ -248,6 +248,7 @@ static int32        fingwait;
 static Lock    gclock;
 
 static void    runfinq(void);
+static void    wakefing(void);
 static void    bgsweep(void);
 static Workbuf* getempty(Workbuf*);
 static Workbuf* getfull(Workbuf*);
@@ -1880,6 +1881,7 @@ static struct
 {
        G*      g;
        bool    parked;
+       uint32  lastsweepgen;
 
        MSpan** spans;
        uint32  nspan;
@@ -1894,18 +1896,18 @@ bgsweep(void)
        for(;;) {
                while(runtime·sweepone() != -1) {
                        gcstats.nbgsweep++;
+                       if(sweep.lastsweepgen != runtime·mheap.sweepgen) {
+                               // If bgsweep does not catch up for any reason
+                               // (does not finish before next GC),
+                               // we still need to kick off runfinq at least once per GC.
+                               sweep.lastsweepgen = runtime·mheap.sweepgen;
+                               wakefing();
+                       }
                        runtime·gosched();
                }
+               // kick off goroutine to run queued finalizers
+               wakefing();
                runtime·lock(&gclock);
-               if(finq != nil) {
-                       // kick off or wake up goroutine to run queued finalizers
-                       if(fing == nil)
-                               fing = runtime·newproc1(&runfinqv, nil, 0, 0, runtime·gc);
-                       else if(fingwait) {
-                               fingwait = 0;
-                               runtime·ready(fing);
-                       }
-               }
                if(!runtime·mheap.sweepdone) {
                        // It's possible if GC has happened between sweepone has
                        // returned -1 and gclock lock.
@@ -2257,17 +2259,8 @@ runtime·gc(int32 force)
 
        // now that gc is done, kick off finalizer thread if needed
        if(!ConcurrentSweep) {
-               if(finq != nil) {
-                       runtime·lock(&gclock);
-                       // kick off or wake up goroutine to run queued finalizers
-                       if(fing == nil)
-                               fing = runtime·newproc1(&runfinqv, nil, 0, 0, runtime·gc);
-                       else if(fingwait) {
-                               fingwait = 0;
-                               runtime·ready(fing);
-                       }
-                       runtime·unlock(&gclock);
-               }
+               // kick off goroutine to run queued finalizers
+               wakefing();
                // give the queued finalizers, if any, a chance to run
                runtime·gosched();
        }
@@ -2621,6 +2614,22 @@ runfinq(void)
        }
 }
 
+static void
+wakefing(void)
+{
+       if(finq == nil)
+               return;
+       runtime·lock(&gclock);
+       // kick off or wake up goroutine to run queued finalizers
+       if(fing == nil)
+               fing = runtime·newproc1(&runfinqv, nil, 0, 0, runtime·gc);
+       else if(fingwait) {
+               fingwait = 0;
+               runtime·ready(fing);
+       }
+       runtime·unlock(&gclock);
+}
+
 void
 runtime·marknogc(void *v)
 {