tlibthread: fix pthreadperthread bugs - plan9port - [fork] Plan 9 from user space
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---
DIR commit b73633b1b4e9d3dbd680edf900b2b53befbf5a9a
DIR parent b3a20a96eb2b91a5b0b8a8fb506e20a2fb50ebe8
HTML Author: Russ Cox <rsc@swtch.com>
Date: Wed, 30 Dec 2020 00:15:37 -0500
libthread: fix pthreadperthread bugs
Diffstat:
M src/libthread/thread.c | 293 ++++++++++++++++++++-----------
M src/libthread/threadimpl.h | 1 +
2 files changed, 187 insertions(+), 107 deletions(-)
---
DIR diff --git a/src/libthread/thread.c b/src/libthread/thread.c
t@@ -1,6 +1,6 @@
#include "threadimpl.h"
-int _threaddebuglevel;
+int _threaddebuglevel = 0;
static uint threadnproc;
static uint threadnsysproc;
t@@ -20,13 +20,16 @@ static void contextswitch(Context *from, Context *to);
static void procmain(Proc*);
static void procscheduler(Proc*);
static int threadinfo(void*, char*);
+static void pthreadscheduler(Proc *p);
+static void pthreadsleepschedlocked(Proc *p, _Thread *t);
+static void pthreadwakeupschedlocked(Proc *p, _Thread *self, _Thread *t);
+static _Thread* procnext(Proc*, _Thread*);
static void
-_threaddebug(char *fmt, ...)
+_threaddebug(_Thread *t, char *fmt, ...)
{
va_list arg;
char buf[128];
- _Thread *t;
char *p;
static int fd = -1;
t@@ -52,7 +55,8 @@ _threaddebug(char *fmt, ...)
va_start(arg, fmt);
vsnprint(buf, sizeof buf, fmt, arg);
va_end(arg);
- t = proc()->thread;
+ if(t == nil)
+ t = proc()->thread;
if(t)
fprint(fd, "%p %d.%d: %s\n", proc(), getpid(), t->id, buf);
else
t@@ -181,10 +185,15 @@ _threadcreate(Proc *p, void (*fn)(void*), void *arg, uint stack)
stack = 0; // not using it
t = threadalloc(fn, arg, stack);
t->proc = p;
- if(p->nthread == 0)
- p->thread0 = t;
- else if(pthreadperthread)
- _threadpthreadstart(p, t);
+ if(pthreadperthread) {
+ if(p->nthread != 0)
+ _threadpthreadstart(p, t);
+ else
+ t->mainthread = 1;
+ } else {
+ if(p->nthread == 0)
+ p->thread0 = t;
+ }
p->nthread++;
addthreadinproc(p, t);
_threadready(t);
t@@ -197,6 +206,7 @@ threadcreate(void (*fn)(void*), void *arg, uint stack)
_Thread *t;
t = _threadcreate(proc(), fn, arg, stack);
+ _threaddebug(nil, "threadcreate %d", t->id);
return t->id;
}
t@@ -210,41 +220,11 @@ proccreate(void (*fn)(void*), void *arg, uint stack)
p = procalloc();
t = _threadcreate(p, fn, arg, stack);
id = t->id; /* t might be freed after _procstart */
+ _threaddebug(t, "proccreate %p", p);
_procstart(p, procmain);
return id;
}
-// For pthreadperthread mode, procswitch flips
-// between the threads.
-static void
-procswitch(Proc *p, _Thread *from, _Thread *to)
-{
- _threaddebug("procswitch %p %d %d", p, from?from->id:-1, to?to->id:-1);
- lock(&p->schedlock);
- from->schedrend.l = &p->schedlock;
- if(to) {
- p->schedthread = to;
- to->schedrend.l = &p->schedlock;
- _threaddebug("procswitch wakeup %p %d", p, to->id);
- _procwakeup(&to->schedrend);
- }
- if(p->schedthread != from) {
- if(from->exiting) {
- unlock(&p->schedlock);
- _threadpexit();
- _threaddebug("procswitch exit wakeup!!!\n");
- }
- while(p->schedthread != from) {
- _threaddebug("procswitch sleep %p %d", p, from->id);
- _procsleep(&from->schedrend);
- _threaddebug("procswitch awake %p %d", p, from->id);
- }
- if(p->schedthread != from)
- sysfatal("_procswitch %p %p oops", p->schedthread, from);
- }
- unlock(&p->schedlock);
-}
-
void
_threadswitch(void)
{
t@@ -255,10 +235,10 @@ _threadswitch(void)
/*print("threadswtch %p\n", p); */
- if(p->thread == p->thread0)
+ if(pthreadperthread)
+ pthreadscheduler(p);
+ else if(p->thread == p->thread0)
procscheduler(p);
- else if(pthreadperthread)
- procswitch(p, p->thread, p->thread0);
else
contextswitch(&p->thread->context, &p->schedcontext);
}
t@@ -390,7 +370,10 @@ void
_threadpthreadmain(Proc *p, _Thread *t)
{
_threadsetproc(p);
- procswitch(p, t, nil);
+ lock(&p->lock);
+ pthreadsleepschedlocked(p, t);
+ unlock(&p->lock);
+ _threaddebug(nil, "startfn");
t->startfn(t->startarg);
threadexits(nil);
}
t@@ -400,76 +383,47 @@ procscheduler(Proc *p)
{
_Thread *t;
- _threaddebug("scheduler enter");
+ _threaddebug(nil, "scheduler enter");
//print("s %p\n", p);
-Top:
- lock(&p->lock);
- t = p->thread;
- p->thread = nil;
- if(t->exiting){
- delthreadinproc(p, t);
- p->nthread--;
-/*print("nthread %d\n", p->nthread); */
- _threadstkfree(t->stk, t->stksize);
- /*
- * Cannot free p->thread0 yet: it is used for the
- * context switches back to the scheduler.
- * Instead, we will free it at the end of this function.
- * But all the other threads can be freed now.
- */
- if(t != p->thread0)
- free(t);
- }
-
- for(;;){
- if((t = p->pinthread) != nil){
- while(!onlist(&p->runqueue, t)){
- p->runrend.l = &p->lock;
- _threaddebug("scheduler sleep (pin)");
- _procsleep(&p->runrend);
- _threaddebug("scheduler wake (pin)");
- }
- }else
- while((t = p->runqueue.head) == nil){
- if(p->nthread == 0)
- goto Out;
- if((t = p->idlequeue.head) != nil){
- /*
- * Run all the idling threads once.
- */
- while((t = p->idlequeue.head) != nil){
- delthread(&p->idlequeue, t);
- addthread(&p->runqueue, t);
- }
- continue;
- }
- p->runrend.l = &p->lock;
- _threaddebug("scheduler sleep");
- _procsleep(&p->runrend);
- _threaddebug("scheduler wake");
+ for(;;) {
+ /* Finish running current thread. */
+ lock(&p->lock);
+ t = p->thread;
+ p->thread = nil;
+ if(t->exiting){
+ delthreadinproc(p, t);
+ p->nthread--;
+ /*print("nthread %d\n", p->nthread); */
+ _threadstkfree(t->stk, t->stksize);
+ /*
+ * Cannot free p->thread0 yet: it is used for the
+ * context switches back to the scheduler.
+ * Instead, we will free it at the end of this function.
+ * But all the other threads can be freed now.
+ */
+ if(t != p->thread0)
+ free(t);
}
- if(p->pinthread && p->pinthread != t)
- fprint(2, "p->pinthread %p t %p\n", p->pinthread, t);
- assert(p->pinthread == nil || p->pinthread == t);
- delthread(&p->runqueue, t);
+
+ /* Pick next thread. */
+ t = procnext(p, nil);
+ if(t == nil)
+ break;
+ _threaddebug(nil, "run %d (%s)", t->id, t->name);
+ //print("run %p %p %p %p\n", t, *(uintptr*)(t->context.uc.mc.sp), t->context.uc.mc.di, t->context.uc.mc.si);
unlock(&p->lock);
- p->thread = t;
- p->nswitch++;
- _threaddebug("run %d (%s)", t->id, t->name);
-//print("run %p %p %p %p\n", t, *(uintptr*)(t->context.uc.mc.sp), t->context.uc.mc.di, t->context.uc.mc.si);
+
+ /* Switch to next thread. */
if(t == p->thread0)
return;
- if(pthreadperthread)
- procswitch(p, p->thread0, t);
- else
- contextswitch(&p->schedcontext, &t->context);
- _threaddebug("back in scheduler");
-/*print("back in scheduler\n"); */
- goto Top;
+ contextswitch(&p->schedcontext, &t->context);
+
+ _threaddebug(nil, "back in scheduler");
+ /*print("back in scheduler\n"); */
}
-Out:
- _threaddebug("scheduler exit");
+ /* No more threads in proc. Clean up. */
+ _threaddebug(nil, "scheduler exit");
if(p->mainproc){
/*
* Stupid bug - on Linux 2.6 and maybe elsewhere,
t@@ -502,6 +456,125 @@ Out:
_threadpexit();
}
+static void
+pthreadsleepschedlocked(Proc *p, _Thread *t)
+{
+ _threaddebug(t, "pthreadsleepsched %p %d", p, t->id);;
+ t->schedrend.l = &p->lock;
+ while(p->schedthread != t)
+ _procsleep(&t->schedrend);
+}
+
+static void
+pthreadwakeupschedlocked(Proc *p, _Thread *self, _Thread *t)
+{
+ _threaddebug(self, "pthreadwakeupschedlocked %p %d", p, t->id);;
+ t->schedrend.l = &p->schedlock;
+ p->schedthread = t;
+ _procwakeup(&t->schedrend);
+}
+
+static void
+pthreadscheduler(Proc *p)
+{
+ _Thread *self, *t;
+
+ _threaddebug(nil, "scheduler");
+ lock(&p->lock);
+ self = p->thread;
+ p->thread = nil;
+ _threaddebug(self, "pausing");
+
+ if(self->exiting) {
+ _threaddebug(self, "exiting");
+ delthreadinproc(p, self);
+ p->nthread--;
+ }
+
+ t = procnext(p, self);
+ if(t != nil) {
+ pthreadwakeupschedlocked(p, self, t);
+ if(!self->exiting) {
+ pthreadsleepschedlocked(p, self);
+ _threaddebug(nil, "resume %d", self->id);
+ unlock(&p->lock);
+ return;
+ }
+ }
+
+ if(t == nil) {
+ /* Tear down proc bookkeeping. Wait to free p. */
+ delproc(p);
+ lock(&threadnproclock);
+ if(p->sysproc)
+ --threadnsysproc;
+ if(--threadnproc == threadnsysproc)
+ threadexitsall(p->msg);
+ unlock(&threadnproclock);
+ }
+
+ /* Tear down pthread. */
+ if(self->mainthread && p->mainproc) {
+ _threaddaemonize();
+ _threaddebug(self, "sleeper");
+ unlock(&p->lock);
+ /*
+ * Avoid bugs with main pthread exiting.
+ * When all procs are gone, threadexitsall above will happen.
+ */
+ for(;;)
+ sleep(60*60*1000);
+ }
+ _threadsetproc(nil);
+ free(self);
+ unlock(&p->lock);
+ if(t == nil)
+ free(p);
+ _threadpexit();
+}
+
+static _Thread*
+procnext(Proc *p, _Thread *self)
+{
+ _Thread *t;
+
+ if((t = p->pinthread) != nil){
+ while(!onlist(&p->runqueue, t)){
+ p->runrend.l = &p->lock;
+ _threaddebug(self, "scheduler sleep (pin)");
+ _procsleep(&p->runrend);
+ _threaddebug(self, "scheduler wake (pin)");
+ }
+ } else
+ while((t = p->runqueue.head) == nil){
+ if(p->nthread == 0)
+ return nil;
+ if((t = p->idlequeue.head) != nil){
+ /*
+ * Run all the idling threads once.
+ */
+ while((t = p->idlequeue.head) != nil){
+ delthread(&p->idlequeue, t);
+ addthread(&p->runqueue, t);
+ }
+ continue;
+ }
+ p->runrend.l = &p->lock;
+ _threaddebug(self, "scheduler sleep");
+ _procsleep(&p->runrend);
+ _threaddebug(self, "scheduler wake");
+ }
+
+ if(p->pinthread && p->pinthread != t)
+ fprint(2, "p->pinthread %p t %p\n", p->pinthread, t);
+ assert(p->pinthread == nil || p->pinthread == t);
+ delthread(&p->runqueue, t);
+
+ p->thread = t;
+ p->nswitch++;
+ return t;
+}
+
void
_threadsetsysproc(void)
{
t@@ -784,14 +857,18 @@ threadrwakeup(Rendez *r, int all, ulong pc)
int i;
_Thread *t;
+ _threaddebug(nil, "rwakeup %p %d", r, all);
for(i=0;; i++){
if(i==1 && !all)
break;
if((t = r->waiting.head) == nil)
break;
+ _threaddebug(nil, "rwakeup %p %d -> wake %d", r, all, t->id);
delthread(&r->waiting, t);
_threadready(t);
+ _threaddebug(nil, "rwakeup %p %d -> loop", r, all);
}
+ _threaddebug(nil, "rwakeup %p %d -> total %d", r, all, i);
return i;
}
t@@ -827,6 +904,7 @@ int
main(int argc, char **argv)
{
Proc *p;
+ _Thread *t;
char *opts;
argv0 = argv[0];
t@@ -875,7 +953,8 @@ main(int argc, char **argv)
if(mainstacksize == 0)
mainstacksize = 256*1024;
atnotify(threadinfo, 1);
- _threadcreate(p, threadmainstart, nil, mainstacksize);
+ t = _threadcreate(p, threadmainstart, nil, mainstacksize);
+ t->mainthread = 1;
procmain(p);
sysfatal("procscheduler returned in threadmain!");
/* does not return */
DIR diff --git a/src/libthread/threadimpl.h b/src/libthread/threadimpl.h
t@@ -97,6 +97,7 @@ struct _Thread
uchar *stk;
uint stksize;
int exiting;
+ int mainthread;
Proc *proc;
char name[256];
char state[256];