| changeset 5848: | 381f1cb08002 |
|---|---|
| parent 5847: | f0c30306e7d5 |
| child 5849: | 4dd0bcaddc91 |
| author: | cinap_lenrek@felloff.net |
| date: | Wed, 29 Mar 2017 00:30:53 +0200 |
| files: | sys/src/9/port/edf.c sys/src/9/port/portclock.c sys/src/9/port/portdat.h sys/src/9/port/portfns.h sys/src/9/port/proc.c |
| description: | kernel: fix twakeup()/timerdel() race condition timerdel() did not make sure that the timer function is not active (on another cpu). just acquiering the Timer lock in the timer function only blocks the caller of timerdel()/timeradd() but not the other way arround (on a multiprocessor). this changes the timer code to track activity of the timer function, having timerdel() wait until the timer has finished executing. |
1.1--- a/sys/src/9/port/edf.c 1.2+++ b/sys/src/9/port/edf.c 1.3@@ -207,7 +207,7 @@ release(Proc *p) 1.4 } 1.5 1.6 static void 1.7-releaseintr(Ureg*, Timer *t) 1.8+releaseintr(Ureg *u, Timer *t) 1.9 { 1.10 Proc *p; 1.11 extern int panicking; 1.12@@ -254,9 +254,7 @@ releaseintr(Ureg*, Timer *t) 1.13 case Wakeme: 1.14 release(p); 1.15 edfunlock(); 1.16- if(p->trend) 1.17- wakeup(p->trend); 1.18- p->trend = nil; 1.19+ twakeup(u, t); 1.20 if(up){ 1.21 up->delaysched++; 1.22 delayedscheds++; 1.23@@ -445,8 +443,7 @@ edfstop(Proc *p) 1.24 if(p->trace && (pt = proctrace)) 1.25 pt(p, SExpel, 0); 1.26 e->flags &= ~Admitted; 1.27- if(e->tt) 1.28- timerdel(e); 1.29+ timerdel(e); 1.30 edfunlock(); 1.31 } 1.32 } 1.33@@ -479,20 +476,23 @@ edfyield(void) 1.34 e->r = e->t; 1.35 e->flags |= Yield; 1.36 e->d = now; 1.37- if (up->tt == nil){ 1.38- n = e->t - now; 1.39- if(n < 20) 1.40- n = 20; 1.41- up->tns = 1000LL * n; 1.42- up->tf = releaseintr; 1.43- up->tmode = Trelative; 1.44- up->ta = up; 1.45- up->trend = &up->sleep; 1.46- timeradd(up); 1.47- }else if(up->tf != releaseintr) 1.48- print("edfyield: surprise! %#p\n", up->tf); 1.49+ n = e->t - now; 1.50+ if(n < 20) 1.51+ n = 20; 1.52+ up->tns = 1000LL * n; 1.53+ up->tf = releaseintr; 1.54+ up->tmode = Trelative; 1.55+ up->ta = up; 1.56+ up->trend = &up->sleep; 1.57+ timeradd(up); 1.58 edfunlock(); 1.59+ if(waserror()){ 1.60+ up->trend = nil; 1.61+ timerdel(up); 1.62+ nexterror(); 1.63+ } 1.64 sleep(&up->sleep, yfn, nil); 1.65+ poperror(); 1.66 } 1.67 1.68 int
2.1--- a/sys/src/9/port/portclock.c 2.2+++ b/sys/src/9/port/portclock.c 2.3@@ -112,9 +112,13 @@ timeradd(Timer *nt) 2.4 void 2.5 timerdel(Timer *dt) 2.6 { 2.7+ Mach *mp; 2.8 Timers *tt; 2.9 uvlong when; 2.10 2.11+ /* avoid Tperiodic getting re-added */ 2.12+ dt->tmode = Trelative; 2.13+ 2.14 ilock(dt); 2.15 if(tt = dt->tt){ 2.16 ilock(tt); 2.17@@ -123,7 +127,16 @@ timerdel(Timer *dt) 2.18 timerset(tt->head->twhen); 2.19 iunlock(tt); 2.20 } 2.21+ if((mp = dt->tactive) == nil || mp->machno == m->machno){ 2.22+ iunlock(dt); 2.23+ return; 2.24+ } 2.25 iunlock(dt); 2.26+ 2.27+ /* rare, but tf can still be active on another cpu */ 2.28+ while(dt->tactive == mp && dt->tt == nil) 2.29+ if(up->nlocks == 0 && islo()) 2.30+ sched(); 2.31 } 2.32 2.33 void 2.34@@ -190,12 +203,14 @@ timerintr(Ureg *u, Tval) 2.35 tt->head = t->tnext; 2.36 assert(t->tt == tt); 2.37 t->tt = nil; 2.38+ t->tactive = MACHP(m->machno); 2.39 fcallcount[m->machno]++; 2.40 iunlock(tt); 2.41 if(t->tf) 2.42 (*t->tf)(u, t); 2.43 else 2.44 callhzclock++; 2.45+ t->tactive = nil; 2.46 ilock(tt); 2.47 if(t->tmode == Tperiodic) 2.48 tadd(tt, t);
3.1--- a/sys/src/9/port/portdat.h 3.2+++ b/sys/src/9/port/portdat.h 3.3@@ -556,6 +556,7 @@ struct Timer 3.4 void *ta; 3.5 /* Internal */ 3.6 Lock; 3.7+ Mach *tactive; /* The cpu that tf is active on */ 3.8 Timers *tt; /* Timers queue this timer runs on */ 3.9 Tval tticks; /* tns converted to ticks */ 3.10 Tval twhen; /* ns represented in fastticks */
4.1--- a/sys/src/9/port/portfns.h 4.2+++ b/sys/src/9/port/portfns.h 4.3@@ -348,6 +348,7 @@ void todinit(void); 4.4 void todset(vlong, vlong, int); 4.5 Block* trimblock(Block*, int, int); 4.6 void tsleep(Rendez*, int (*)(void*), void*, ulong); 4.7+void twakeup(Ureg*, Timer *); 4.8 int uartctl(Uart*, char*); 4.9 int uartgetc(void); 4.10 void uartkick(void*);
5.1--- a/sys/src/9/port/proc.c 5.2+++ b/sys/src/9/port/proc.c 5.3@@ -822,28 +822,17 @@ tfn(void *arg) 5.4 return up->trend == nil || up->tfn(arg); 5.5 } 5.6 5.7-static void 5.8+void 5.9 twakeup(Ureg*, Timer *t) 5.10 { 5.11 Proc *p; 5.12 Rendez *trend; 5.13 5.14- ilock(t); 5.15 p = t->ta; 5.16 trend = p->trend; 5.17 if(trend != nil){ 5.18+ p->trend = nil; 5.19 wakeup(trend); 5.20- p->trend = nil; 5.21- } 5.22- iunlock(t); 5.23-} 5.24- 5.25-static void 5.26-stoptimer(void) 5.27-{ 5.28- if(up->trend != nil){ 5.29- up->trend = nil; 5.30- timerdel(up); 5.31 } 5.32 } 5.33 5.34@@ -864,11 +853,13 @@ tsleep(Rendez *r, int (*fn)(void*), void 5.35 timeradd(up); 5.36 5.37 if(waserror()){ 5.38- stoptimer(); 5.39+ up->trend = nil; 5.40+ timerdel(up); 5.41 nexterror(); 5.42 } 5.43 sleep(r, tfn, arg); 5.44- stoptimer(); 5.45+ up->trend = nil; 5.46+ timerdel(up); 5.47 poperror(); 5.48 } 5.49 5.50@@ -1102,8 +1093,7 @@ pexit(char *exitstr, int freemem) 5.51 void (*pt)(Proc*, int, vlong); 5.52 5.53 up->alarm = 0; 5.54- if(up->tt != nil) 5.55- timerdel(up); 5.56+ timerdel(up); 5.57 pt = proctrace; 5.58 if(pt != nil) 5.59 pt(up, SDead, 0);