Module: xenomai-forge
Branch: master
Commit: 8e7a1ef2672b145358da14628a1a4a69c21bd53c
URL:
http://git.xenomai.org/?p=xenomai-forge.git;a=commit;h=8e7a1ef2672b145358da14628a1a4a69c21bd53c
Author: Philippe Gerum <r...@xenomai.org>
Date: Sun Dec 4 19:16:12 2011 +0100
cobalt/monitor: plug signal leakage on entry to wait op
A thread about to wait for a GRANT/DRAIN signal might have sent a
signal prior to running the syscall (usually the converse one). We
must wake any satisfied sleeper prior to entering sleep.
In additional, the wakeup code for the DRAIN signal has been fixed
(inverted test of the drain wait list).
---
kernel/cobalt/monitor.c | 25 ++++++++++++++++++++-----
1 files changed, 20 insertions(+), 5 deletions(-)
diff --git a/kernel/cobalt/monitor.c b/kernel/cobalt/monitor.c
index d6f807e..4e4ea4f 100644
--- a/kernel/cobalt/monitor.c
+++ b/kernel/cobalt/monitor.c
@@ -166,6 +166,11 @@ static int cobalt_monitor_wakeup(struct cobalt_monitor
*mon)
struct xnholder *h;
pthread_t tid;
+ /*
+ * Having the GRANT signal pending does not necessarily mean
+ * that somebody is actually waiting for it, so we have to
+ * check both conditions below.
+ */
if ((datp->flags & COBALT_MONITOR_GRANTED) == 0 ||
emptyq_p(&mon->waiters))
goto drain;
@@ -202,11 +207,11 @@ static int cobalt_monitor_wakeup(struct cobalt_monitor
*mon)
}
drain:
/*
- * Unblock threads waiting for a drain event, either one or
- * all, depending on the broadcast bit.
+ * Unblock threads waiting for a drain event if that signal is
+ * pending, either one or all, depending on the broadcast bit.
*/
if ((datp->flags & COBALT_MONITOR_DRAINED) != 0 &&
- !xnsynch_pended_p(&mon->drain)) {
+ xnsynch_pended_p(&mon->drain)) {
if (datp->flags & COBALT_MONITOR_BROADCAST)
resched |= xnsynch_flush(&mon->drain, 0)
== XNSYNCH_RESCHED;
@@ -228,6 +233,7 @@ int cobalt_monitor_wait(struct cobalt_monitor_shadow __user
*u_monsh,
int __user *u_ret)
{
pthread_t cur = cobalt_current_thread();
+ struct cobalt_monitor_data *datp;
struct cobalt_monitor *mon = NULL;
xnticks_t timeout = XN_INFINITE;
xntmode_t tmode = XN_RELATIVE;
@@ -254,6 +260,15 @@ int cobalt_monitor_wait(struct cobalt_monitor_shadow
__user *u_monsh,
goto out;
}
+ /*
+ * The current thread might have sent signals to the monitor
+ * it wants to sleep on: wake up satisfied waiters before
+ * going to sleep.
+ */
+ datp = mon->data;
+ if (datp->flags & COBALT_MONITOR_SIGNALED)
+ cobalt_monitor_wakeup(mon);
+
/* Release the gate prior to waiting, all atomically. */
xnsynch_release(&mon->gate, &cur->threadbase);
@@ -264,7 +279,7 @@ int cobalt_monitor_wait(struct cobalt_monitor_shadow __user
*u_monsh,
*cur->threadbase.u_mode &= ~XNGRANT;
appendq(&mon->waiters, &cur->monitor_link);
}
- mon->data->flags |= COBALT_MONITOR_PENDED;
+ datp->flags |= COBALT_MONITOR_PENDED;
info = xnsynch_sleep_on(synch, timeout, tmode);
if (info) {
@@ -279,7 +294,7 @@ int cobalt_monitor_wait(struct cobalt_monitor_shadow __user
*u_monsh,
removeq(&mon->waiters, &cur->monitor_link);
if (emptyq_p(&mon->waiters) && !xnsynch_pended_p(&mon->drain))
- mon->data->flags &= ~COBALT_MONITOR_PENDED;
+ datp->flags &= ~COBALT_MONITOR_PENDED;
if (info & XNBREAK)
opret = -EINTR;
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