From: george anzinger <george@mvista.com>
The attached patch should fix the system hang referenced below (works
on my system) and also the deliver to a specific thread issue. I
don't have a test for this last issue so feed back is desired. Once
you pass it I will send it in.
Ulrich Drepper wrote:
>
> http://people.redhat.com/drepper/t-overr.bz2
>
> is a statically linked binary. You'll see that the program hangs when
> it tries to disarm the timer.
include/linux/sched.h | 1
kernel/posix-timers.c | 68 +++++++++++++++++++++++++++++++-------------------
kernel/signal.c | 2 -
3 files changed, 45 insertions(+), 26 deletions(-)
diff -puN include/linux/sched.h~posix-timer-hang-fix include/linux/sched.h
--- 25/include/linux/sched.h~posix-timer-hang-fix 2003-04-02 23:46:41.000000000 -0800
+++ 25-akpm/include/linux/sched.h 2003-04-02 23:46:41.000000000 -0800
@@ -546,6 +546,7 @@ extern void block_all_signals(int (*noti
extern void unblock_all_signals(void);
extern void release_task(struct task_struct * p);
extern int send_sig_info(int, struct siginfo *, struct task_struct *);
+extern int specific_send_sig_info(int, struct siginfo *, struct task_struct *);
extern int force_sig_info(int, struct siginfo *, struct task_struct *);
extern int __kill_pg_info(int sig, struct siginfo *info, pid_t pgrp);
extern int kill_pg_info(int, struct siginfo *, pid_t);
diff -puN kernel/posix-timers.c~posix-timer-hang-fix kernel/posix-timers.c
--- 25/kernel/posix-timers.c~posix-timer-hang-fix 2003-04-02 23:46:41.000000000 -0800
+++ 25-akpm/kernel/posix-timers.c 2003-04-02 23:46:41.000000000 -0800
@@ -77,6 +77,20 @@ static spinlock_t idr_lock = SPIN_LOCK_U
# define timer_active(tmr) BARFY // error to use outside of SMP
# define set_timer_inactive(tmr) do { } while (0)
#endif
+
+/*
+ * For some reason mips/mips64 define the SIGEV constants plus 128.
+ * Here we define a mask to get rid of the common bits. The
+ * optimizer should make this costless to all but mips.
+ */
+#if (ARCH == mips) || (ARCH == mips64)
+#define MIPS_SIGEV ~(SIGEV_NONE & \
+ SIGEV_SIGNAL & \
+ SIGEV_THREAD & \
+ SIGEV_THREAD_ID)
+#else
+#define MIPS_SIGEV (int)-1
+#endif
/*
* The timer ID is turned into a timer address by idr_find().
* Verifying a valid ID consists of:
@@ -225,10 +239,9 @@ static void schedule_next_timer(struct k
struct now_struct now;
/* Set up the timer for the next interval (if there is one) */
- if (!timr->it_incr) {
- set_timer_inactive(timr);
+ if (!timr->it_incr)
return;
- }
+
posix_get_now(&now);
do {
posix_bump_timer(timr);
@@ -258,7 +271,7 @@ void do_schedule_next_timer(struct sigin
timr = lock_timer(info->si_tid, &flags);
- if (!timr || !timr->it_requeue_pending)
+ if (!timr || timr->it_requeue_pending != info->si_sys_private)
goto exit;
schedule_next_timer(timr);
@@ -276,7 +289,17 @@ exit:
* indicating that the signal was either not queued or was queued
* without an info block. In this case, we will not get a call back to
* do_schedule_next_timer() so we do it here. This should be rare...
+
+ * An interesting problem can occure if, while a signal, and thus a call
+ * back is pending, the timer is rearmed, i.e. stopped and restarted.
+ * We then need to sort out the call back and do the right thing. What
+ * we do is to put a counter in the info block and match it with the
+ * timers copy on the call back. If they don't match, we just ignore
+ * the call back. Note that we do allow the timer to be deleted while
+ * a signal is pending. The standard says we can allow that signal to
+ * be delivered, and we do.
*/
+static int pendcount;
static void timer_notify_task(struct k_itimer *timr)
{
@@ -291,12 +314,20 @@ static void timer_notify_task(struct k_i
info.si_code = SI_TIMER;
info.si_tid = timr->it_id;
info.si_value = timr->it_sigev_value;
- if (!timr->it_incr)
- set_timer_inactive(timr);
- else
- timr->it_requeue_pending = info.si_sys_private = 1;
-
- ret = send_sig_info(info.si_signo, &info, timr->it_process);
+ if( !++pendcount ) ++pendcount;
+ if (timr->it_incr){
+ /*
+ * Don't allow a call back counter of zero...
+ */
+ if( !++pendcount )
+ ++pendcount;
+ timr->it_requeue_pending = info.si_sys_private = pendcount;
+ }
+ if( timr->it_sigev_notify & SIGEV_THREAD_ID & MIPS_SIGEV){
+ ret = specific_send_sig_info(info.si_signo, &info,
+ timr->it_process);
+ }else
+ ret = send_sig_info(info.si_signo, &info, timr->it_process);
switch (ret) {
default:
@@ -332,23 +363,11 @@ static void posix_timer_fn(unsigned long
unsigned long flags;
spin_lock_irqsave(&timr->it_lock, flags);
+ set_timer_inactive(timr);
timer_notify_task(timr);
unlock_timer(timr, flags);
}
-/*
- * For some reason mips/mips64 define the SIGEV constants plus 128.
- * Here we define a mask to get rid of the common bits. The
- * optimizer should make this costless to all but mips.
- */
-#if (ARCH == mips) || (ARCH == mips64)
-#define MIPS_SIGEV ~(SIGEV_NONE & \
- SIGEV_SIGNAL & \
- SIGEV_THREAD & \
- SIGEV_THREAD_ID)
-#else
-#define MIPS_SIGEV (int)-1
-#endif
static inline struct task_struct * good_sigevent(sigevent_t * event)
{
@@ -847,8 +866,7 @@ static inline int do_timer_delete(struct
{
timer->it_incr = 0;
#ifdef CONFIG_SMP
- if (timer_active(timer) &&
- !del_timer(&timer->it_timer) && !timer->it_requeue_pending)
+ if (timer_active(timer) && !del_timer(&timer->it_timer))
/*
* It can only be active if on an other cpu. Since
* we have cleared the interval stuff above, it should
diff -puN kernel/signal.c~posix-timer-hang-fix kernel/signal.c
--- 25/kernel/signal.c~posix-timer-hang-fix 2003-04-02 23:46:41.000000000 -0800
+++ 25-akpm/kernel/signal.c 2003-04-02 23:46:41.000000000 -0800
@@ -749,7 +749,7 @@ out_set:
(((sig) < SIGRTMIN) && sigismember(&(sigptr)->signal, (sig)))
-static int
+int
specific_send_sig_info(int sig, struct siginfo *info, struct task_struct *t)
{
int ret = 0;
_