selwakeup() does a filtered wakeup because all threads waiting in
poll(2) or select(2) are blocking on the same wait channel.
The wakeup is currently implemented by first grabbing a reference
to a thread via tfind(). This makes removing the KERNEL_LOCK()
complicated because we need to ensure the thread isn't disappearing
while we want to wake it up.
We can instead rely on a single datastructure: the global sleep queue.
That's what the diff below does, ok?
Index: kern/kern_synch.c
===================================================================
RCS file: /cvs/src/sys/kern/kern_synch.c,v
retrieving revision 1.148
diff -u -p -r1.148 kern_synch.c
--- kern/kern_synch.c 23 Apr 2019 13:35:12 -0000 1.148
+++ kern/kern_synch.c 12 May 2019 18:31:08 -0000
@@ -425,7 +425,7 @@ unsleep(struct proc *p)
* Make a number of processes sleeping on the specified identifier runnable.
*/
void
-wakeup_n(const volatile void *ident, int n)
+wakeup_n_id(const volatile void *ident, int n, pid_t tid)
{
struct slpque *qp;
struct proc *p;
@@ -449,24 +449,33 @@ wakeup_n(const volatile void *ident, int
if (p->p_stat != SSLEEP && p->p_stat != SSTOP)
panic("wakeup: p_stat is %d", (int)p->p_stat);
#endif
- if (p->p_wchan == ident) {
+ if (p->p_wchan == ident && (tid == -1 || p->p_tid == tid)) {
--n;
p->p_wchan = 0;
TAILQ_REMOVE(qp, p, p_runq);
if (p->p_stat == SSLEEP)
setrunnable(p);
+ /* Hack for poll(2)/select(2). */
+ if ((tid != -1) && (p->p_flag & P_SELECT))
+ atomic_clearbits_int(&p->p_flag, P_SELECT);
}
}
SCHED_UNLOCK(s);
}
+void
+wakeup_n(const volatile void *ident, int n)
+{
+ wakeup_n_id(ident, n, -1);
+}
+
/*
* Make all processes sleeping on the specified identifier runnable.
*/
void
wakeup(const volatile void *chan)
{
- wakeup_n(chan, -1);
+ wakeup_n_id(chan, -1, -1);
}
int
Index: kern/sys_generic.c
===================================================================
RCS file: /cvs/src/sys/kern/sys_generic.c,v
retrieving revision 1.123
diff -u -p -r1.123 sys_generic.c
--- kern/sys_generic.c 21 Jan 2019 23:41:26 -0000 1.123
+++ kern/sys_generic.c 12 May 2019 18:30:24 -0000
@@ -789,8 +789,7 @@ selrecord(struct proc *selector, struct
void
selwakeup(struct selinfo *sip)
{
- struct proc *p;
- int s;
+ pid_t tid;
KNOTE(&sip->si_note, NOTE_SUBMIT);
if (sip->si_seltid == 0)
@@ -800,19 +799,9 @@ selwakeup(struct selinfo *sip)
sip->si_flags &= ~SI_COLL;
wakeup(&selwait);
}
- p = tfind(sip->si_seltid);
+ tid = sip->si_seltid;
sip->si_seltid = 0;
- if (p != NULL) {
- SCHED_LOCK(s);
- if (p->p_wchan == (caddr_t)&selwait) {
- if (p->p_stat == SSLEEP)
- setrunnable(p);
- else
- unsleep(p);
- } else if (p->p_flag & P_SELECT)
- atomic_clearbits_int(&p->p_flag, P_SELECT);
- SCHED_UNLOCK(s);
- }
+ wakeup_n_id(&selwait, 1, tid);
}
void
Index: sys/systm.h
===================================================================
RCS file: /cvs/src/sys/sys/systm.h,v
retrieving revision 1.141
diff -u -p -r1.141 systm.h
--- sys/systm.h 23 Apr 2019 13:35:12 -0000 1.141
+++ sys/systm.h 12 May 2019 18:25:02 -0000
@@ -261,6 +261,7 @@ void cond_signal(struct cond *);
struct mutex;
struct rwlock;
+void wakeup_n_id(const volatile void *, int, pid_t);
void wakeup_n(const volatile void *, int);
void wakeup(const volatile void *);
#define wakeup_one(c) wakeup_n((c), 1)
