Currently, dopselect() and doppoll() call tsleep_nsec() without retry.
cheloha@ asked if the functions should handle spurious wakeups. I guess
such wakeups are unlikely with the nowake wait channel, but I am not
sure if that is a safe guess.
The following diff adds the retrying. The code is a bit arduous, so the
retry loop is put in a separate function that both poll and select use.
Index: kern/sys_generic.c
===================================================================
RCS file: src/sys/kern/sys_generic.c,v
retrieving revision 1.141
diff -u -p -r1.141 sys_generic.c
--- kern/sys_generic.c 16 Nov 2021 13:48:23 -0000 1.141
+++ kern/sys_generic.c 16 Nov 2021 13:50:08 -0000
@@ -90,6 +90,7 @@ int dopselect(struct proc *, int, fd_set
int doppoll(struct proc *, struct pollfd *, u_int, struct timespec *,
const sigset_t *, register_t *);
void doselwakeup(struct selinfo *);
+int selsleep(struct timespec *);
int
iovec_copyin(const struct iovec *uiov, struct iovec **iovp, struct iovec *aiov,
@@ -664,19 +665,7 @@ dopselect(struct proc *p, int nd, fd_set
* there's nothing to wait for.
*/
if (nevents == 0 && ncollected == 0) {
- uint64_t nsecs = INFSLP;
-
- if (timeout != NULL) {
- if (!timespecisset(timeout))
- goto done;
- nsecs = MAX(1, MIN(TIMESPEC_TO_NSEC(timeout), MAXTSLP));
- }
- error = tsleep_nsec(&nowake, PSOCK | PCATCH, "kqsel", nsecs);
- /* select is not restarted after signals... */
- if (error == ERESTART)
- error = EINTR;
- if (error == EWOULDBLOCK)
- error = 0;
+ error = selsleep(timeout);
goto done;
}
@@ -849,6 +838,46 @@ selfalse(dev_t dev, int events, struct p
}
/*
+ * Sleep until a signal arrives or the optional timeout expires.
+ */
+int
+selsleep(struct timespec *timeout)
+{
+ uint64_t end, now, nsecs;
+ int error;
+
+ if (timeout != NULL) {
+ if (!timespecisset(timeout))
+ return (0);
+ now = getnsecuptime();
+ end = MIN(now + TIMESPEC_TO_NSEC(timeout), MAXTSLP);
+ if (end < now)
+ end = MAXTSLP;
+ }
+
+ do {
+ if (timeout != NULL)
+ nsecs = MAX(1, end - now);
+ else
+ nsecs = INFSLP;
+ error = tsleep_nsec(&nowake, PSOCK | PCATCH, "selslp", nsecs);
+ if (timeout != NULL) {
+ now = getnsecuptime();
+ if (now >= end)
+ break;
+ }
+ } while (error == 0);
+
+ /* poll/select is not restarted after signals... */
+ if (error == ERESTART)
+ error = EINTR;
+ if (error == EWOULDBLOCK)
+ error = 0;
+
+ return (error);
+}
+
+/*
* Record a select request.
*/
void
@@ -1158,19 +1187,7 @@ doppoll(struct proc *p, struct pollfd *f
* there's nothing to wait for.
*/
if (nevents == 0 && ncollected == 0) {
- uint64_t nsecs = INFSLP;
-
- if (timeout != NULL) {
- if (!timespecisset(timeout))
- goto done;
- nsecs = MAX(1, MIN(TIMESPEC_TO_NSEC(timeout), MAXTSLP));
- }
-
- error = tsleep_nsec(&nowake, PSOCK | PCATCH, "kqpoll", nsecs);
- if (error == ERESTART)
- error = EINTR;
- if (error == EWOULDBLOCK)
- error = 0;
+ error = selsleep(timeout);
goto done;
}
