tvarious bug fixes and paranoia - plan9port - [fork] Plan 9 from user space
HTML git clone git://src.adamsgaard.dk/plan9port
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---
DIR commit 6c7460701e7896446d0fb14bf9b24f258c61b6a6
DIR parent a09e80f9c414ffc815641d49836be3a2a6a07800
HTML Author: rsc <devnull@localhost>
Date: Sun, 23 May 2004 00:59:33 +0000
various bug fixes and paranoia
Diffstat:
M src/lib9/notify.c | 1 +
M src/lib9/qlock.c | 10 ++++++++++
M src/lib9/rendez-signal.c | 146 ++++++++++++++++---------------
3 files changed, 87 insertions(+), 70 deletions(-)
---
DIR diff --git a/src/lib9/notify.c b/src/lib9/notify.c
t@@ -35,6 +35,7 @@ static struct {
SIGVTALRM, 0,
SIGUSR1, 0,
SIGUSR2, 0,
+ SIGWINCH, 1,
#ifdef SIGINFO
SIGINFO, 0,
#endif
DIR diff --git a/src/lib9/qlock.c b/src/lib9/qlock.c
t@@ -13,6 +13,7 @@ enum
QueuingR,
QueuingW,
Sleeping,
+ Waking,
};
static ulong (*_rendezvousp)(ulong, ulong) = rendezvous;
t@@ -74,6 +75,7 @@ qlock(QLock *q)
/* wait */
while((*_rendezvousp)((ulong)mp, 1) == ~0)
;
+ assert(mp->state == Waking);
mp->inuse = 0;
}
t@@ -90,6 +92,7 @@ qunlock(QLock *q)
if(q->head == nil)
q->tail = nil;
unlock(&q->lock);
+ p->state = Waking;
while((*_rendezvousp)((ulong)p, 0x12345) == ~0)
;
return;
t@@ -139,6 +142,7 @@ rlock(RWLock *q)
/* wait in kernel */
while((*_rendezvousp)((ulong)mp, 1) == ~0)
;
+ assert(mp->state == Waking);
mp->inuse = 0;
}
t@@ -180,6 +184,7 @@ runlock(RWLock *q)
unlock(&q->lock);
/* wakeup waiter */
+ p->state = Waking;
while((*_rendezvousp)((ulong)p, 0) == ~0)
;
}
t@@ -212,6 +217,7 @@ wlock(RWLock *q)
/* wait in kernel */
while((*_rendezvousp)((ulong)mp, 1) == ~0)
;
+ assert(mp->state == Waking);
mp->inuse = 0;
}
t@@ -251,6 +257,7 @@ wunlock(RWLock *q)
if(q->head == nil)
q->tail = nil;
unlock(&q->lock);
+ p->state = Waking;
while((*_rendezvousp)((ulong)p, 0) == ~0)
;
return;
t@@ -266,6 +273,7 @@ wunlock(RWLock *q)
p = q->head;
q->head = p->next;
q->readers++;
+ p->state = Waking;
while((*_rendezvousp)((ulong)p, 0) == ~0)
;
}
t@@ -308,6 +316,7 @@ rsleep(Rendez *r)
if(r->l->head == nil)
r->l->tail = nil;
unlock(&r->l->lock);
+ t->state = Waking;
while((*_rendezvousp)((ulong)t, 0x12345) == ~0)
;
}else{
t@@ -318,6 +327,7 @@ rsleep(Rendez *r)
/* wait for a wakeup */
while((*_rendezvousp)((ulong)me, 0x23456) == ~0)
;
+ assert(me->state == Waking);
me->inuse = 0;
if(!r->l->locked){
fprint(2, "rsleep: not locked after wakeup\n");
DIR diff --git a/src/lib9/rendez-signal.c b/src/lib9/rendez-signal.c
t@@ -28,11 +28,14 @@
If a rendezvous is interrupted the return value is ~0, so
that value should not be used in normal communication.
- * This simulates rendezvous with shared memory, pause, and SIGUSR1.
+ * This simulates rendezvous with shared memory, sigsuspend, and SIGUSR1.
*/
+#include <u.h>
#include <signal.h>
-#include <lib9.h>
+#include <libc.h>
+
+#define DBG 0
enum
{
t@@ -43,11 +46,11 @@ typedef struct Vous Vous;
struct Vous
{
Vous *link;
- Lock lk;
int pid;
- int wakeup;
- ulong val;
+ int wokeup;
ulong tag;
+ ulong val1; /* value for the sleeper */
+ ulong val2; /* value for the waker */
};
static void
t@@ -57,9 +60,17 @@ ign(int x)
}
void /*__attribute__((constructor))*/
-ignusr1(void)
+ignusr1(int restart)
{
- signal(SIGUSR1, ign);
+ struct sigaction sa;
+
+ memset(&sa, 0, sizeof sa);
+ sa.sa_handler = ign;
+ sigemptyset(&sa.sa_mask);
+ sigaddset(&sa.sa_mask, SIGUSR1);
+ if(restart)
+ sa.sa_flags = SA_RESTART;
+ sigaction(SIGUSR1, &sa, nil);
}
static Vous vouspool[2048];
t@@ -78,117 +89,112 @@ getvous(void)
vousfree = v->link;
}else if(nvousused < nelem(vouspool))
v = &vouspool[nvousused++];
- else
+ else{
+ fprint(2, "rendezvous: out of vous!\n");
abort();
+ }
return v;
}
static void
putvous(Vous *v)
{
- lock(&vouslock);
v->link = vousfree;
vousfree = v;
- unlock(&vouslock);
}
static Vous*
-findvous(ulong tag, ulong val, int pid)
+findvous(ulong tag)
{
int h;
Vous *v, **l;
- lock(&vouslock);
h = tag%VOUSHASH;
for(l=&voushash[h], v=*l; v; l=&(*l)->link, v=*l){
if(v->tag == tag){
*l = v->link;
- unlock(&vouslock);
+ v->link = nil;
return v;
}
}
+ return nil;
+}
+
+static Vous*
+mkvous(ulong tag)
+{
+ Vous *v;
+ int h;
+
+ h = tag%VOUSHASH;
v = getvous();
- v->pid = pid;
v->link = voushash[h];
- v->val = val;
v->tag = tag;
- lock(&v->lk);
voushash[h] = v;
- unlock(&vouslock);
return v;
}
-#define DBG 0
ulong
rendezvous(ulong tag, ulong val)
{
- int me, vpid;
+ int vpid, pid;
ulong rval;
Vous *v;
sigset_t mask;
- me = getpid();
- v = findvous(tag, val, me);
- if(v->pid == me){
- if(DBG)fprint(2, "pid is %d tag %lux, sleeping\n", me, tag);
+ pid = getpid();
+ lock(&vouslock);
+ if((v = findvous(tag)) == nil){
/*
- * No rendezvous partner was found; the next guy
- * through will find v and wake us, so we must go
- * to sleep.
+ * Go to sleep.
*
- * To go to sleep:
- * 1. disable USR1 signals.
- * 2. unlock v->lk (tells waker okay to signal us).
- * 3. atomically suspend and enable USR1 signals.
- *
- * The call to ignusr1() could be done once at
- * process creation instead of every time through rendezvous.
+ * Block USR1, set the handler to interrupt system calls,
+ * unlock the vouslock so our waker can wake us,
+ * and then suspend.
*/
- v->val = val;
- ignusr1();
- sigprocmask(SIG_SETMASK, NULL, &mask);
+ v = mkvous(tag);
+ v->pid = pid;
+ v->val2 = val;
+ v->wokeup = 0;
+ sigprocmask(SIG_SETMASK, nil, &mask);
sigaddset(&mask, SIGUSR1);
- sigprocmask(SIG_SETMASK, &mask, NULL);
+ sigprocmask(SIG_SETMASK, &mask, nil);
+ ignusr1(0);
+ if(DBG) fprint(2, "%d rv(%lux, %lux) -> s\n", pid, tag, val);
+ unlock(&vouslock);
sigdelset(&mask, SIGUSR1);
- v->wakeup = 0;
- unlock(&v->lk);
- for(;;){
- /*
- * There may well be random signals flying around,
- * so we can't be sure why we woke up. If we weren't
- * properly awakened, we need to go back to sleep.
- */
- sigsuspend(&mask);
- lock(&v->lk); /* do some memory synchronization */
- unlock(&v->lk);
- if(v->wakeup == 1)
- break;
+ sigsuspend(&mask);
+
+ /*
+ * We're awake. Make USR1 not interrupt system calls.
+ * Were we awakened or interrupted?
+ */
+ ignusr1(1);
+ lock(&vouslock);
+ if(v->wokeup){
+ rval = v->val1;
+ if(DBG) fprint(2, "%d rv(%lux, %lux) -> g %lux\n", pid, tag, val, rval);
+ }else{
+ if(findvous(tag) != v){
+ fprint(2, "rendezvous: interrupted but not found in hash table\n");
+ abort();
+ }
+ rval = ~(ulong)0;
+ if(DBG) fprint(2, "%d rv(%lux, %lux) -> g i\n", pid, tag, val);
}
- rval = v->val;
- if(DBG)fprint(2, "pid is %d, awake\n", me);
putvous(v);
+ unlock(&vouslock);
}else{
/*
- * Found someone to meet. Wake him:
- *
- * A. lock v->lk (waits for him to get to his step 2)
- * B. send a USR1
- *
- * He won't get the USR1 until he suspends, which
- * means it must wake him up (it can't get delivered
- * before he sleeps).
+ * Wake up sleeper.
*/
+ rval = v->val2;
+ v->val1 = val;
vpid = v->pid;
- lock(&v->lk);
- rval = v->val;
- v->val = val;
- v->wakeup = 1;
- unlock(&v->lk);
- if(kill(vpid, SIGUSR1) < 0){
- if(DBG)fprint(2, "pid is %d, kill %d failed: %r\n", me, vpid);
- abort();
- }
+ v->wokeup = 1;
+ if(DBG) fprint(2, "%d rv(%lux, %lux) -> g %lux, w %d\n", pid, tag, val, rval, vpid);
+ unlock(&vouslock);
+ kill(vpid, SIGUSR1);
}
return rval;
}
-