[PATCH] One possible bugfix for CLOCK_REALTIME timer.

[Hu, Boris]

 <<posix-abs_timer-bugfix.diff>> George,

There is one bug of CLOCK_REALTIME timer reported by Adam at
http://sources.redhat.com/ml/libc-alpha/2004-05/msg00177.html. 

Here is one possible bugfix and it is against linux-2.6.6. All
TIMER_ABSTIME cloks will be collected in k_clock struct and updated in
sys_clock_settime. Could you review it? Thanks. 


diff -urN -X rt.ia32/base/dontdiff
linux-2.6.6/include/linux/posix-timers.h
linux-2.6.6.dev/include/linux/posix-timers.h
--- linux-2.6.6/include/linux/posix-timers.h	2004-05-10
10:32:29.000000000 +0800
+++ linux-2.6.6.dev/include/linux/posix-timers.h	2004-06-02
10:30:57.000000000 +0800
@@ -1,9 +1,14 @@
 #ifndef _linux_POSIX_TIMERS_H
 #define _linux_POSIX_TIMERS_H
 
+#include <linux/list.h>
+#include <linux/spinlock.h>
+
 struct k_clock {
 	int res;		/* in nano seconds */
-	int (*clock_set) (struct timespec * tp);
+        struct list_head abs_timer_list;
+        spinlock_t abs_timer_lock;
+        int (*clock_set) (struct timespec * tp);
 	int (*clock_get) (struct timespec * tp);
 	int (*nsleep) (int flags,
 		       struct timespec * new_setting,
diff -urN -X rt.ia32/base/dontdiff linux-2.6.6/include/linux/timer.h
linux-2.6.6.dev/include/linux/timer.h
--- linux-2.6.6/include/linux/timer.h	2004-05-10 10:32:54.000000000
+0800
+++ linux-2.6.6.dev/include/linux/timer.h	2004-06-02
19:16:08.000000000 +0800
@@ -9,6 +9,7 @@
 
 struct timer_list {
 	struct list_head entry;
+	struct list_head abs_timer_entry;
 	unsigned long expires;
 
 	spinlock_t lock;
diff -urN -X rt.ia32/base/dontdiff linux-2.6.6/kernel/posix-timers.c
linux-2.6.6.dev/kernel/posix-timers.c
--- linux-2.6.6/kernel/posix-timers.c	2004-05-10 10:32:37.000000000
+0800
+++ linux-2.6.6.dev/kernel/posix-timers.c	2004-06-02
19:12:31.000000000 +0800
@@ -7,6 +7,9 @@
  *
  *			     Copyright (C) 2002 2003 by MontaVista
Software.
  *
+ * 2004-06-01  Fix CLOCK_REALTIME clock/timer TIMER_ABSTIME bug.
+ *                           Copyright (C) 2004 Boris Hu
+ *                            
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
(at
@@ -200,7 +203,9 @@
  */
 static __init int init_posix_timers(void)
 {
-	struct k_clock clock_realtime = {.res = CLOCK_REALTIME_RES };
+	struct k_clock clock_realtime = {.res = CLOCK_REALTIME_RES,
+                .abs_timer_lock = SPIN_LOCK_UNLOCKED

+        };
 	struct k_clock clock_monotonic = {.res = CLOCK_REALTIME_RES,
 		.clock_get = do_posix_clock_monotonic_gettime,
 		.clock_set = do_posix_clock_monotonic_settime
@@ -388,6 +393,7 @@
 		return;
 	}
 	posix_clocks[clock_id] = *new_clock;
+        INIT_LIST_HEAD(&posix_clocks[clock_id].abs_timer_list);
 }
 
 static struct k_itimer * alloc_posix_timer(void)
@@ -843,8 +849,15 @@
 	if (((timr->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE))
{
 		if (timr->it_timer.expires == jiffies)
 			timer_notify_task(timr);
-		else
+		else {
 			add_timer(&timr->it_timer);
+                        if (flags & TIMER_ABSTIME) {
+                                spin_lock(&clock->abs_timer_lock);
+
list_add_tail(&(timr->it_timer.abs_timer_entry),
+
&(clock->abs_timer_list));
+                                spin_unlock(&clock->abs_timer_lock);
+                        }
+                }
 	}
 	return 0;
 }
@@ -1085,16 +1098,61 @@
 sys_clock_settime(clockid_t which_clock, const struct timespec __user
*tp)
 {
 	struct timespec new_tp;
+        struct timespec before, now;
+        struct k_clock *clock;
+        long ret;
+        struct timer_list *timer, *tmp;
+        struct timespec delta;
+        u64 exp = 0;
 
-	if ((unsigned) which_clock >= MAX_CLOCKS ||
+        if ((unsigned) which_clock >= MAX_CLOCKS ||
 					!posix_clocks[which_clock].res)
 		return -EINVAL;
-	if (copy_from_user(&new_tp, tp, sizeof (*tp)))
+
+        clock = &posix_clocks[which_clock];
+
+        if (copy_from_user(&new_tp, tp, sizeof (*tp)))
 		return -EFAULT;
 	if (posix_clocks[which_clock].clock_set)
 		return posix_clocks[which_clock].clock_set(&new_tp);
 
-	return do_sys_settimeofday(&new_tp, NULL);
+        do_posix_gettime(clock, &before);
+        
+	ret = do_sys_settimeofday(&new_tp, NULL);
+
+        /*
+         * Check if there exist TIMER_ABSTIME timers to update.
+         */
+        if (which_clock != CLOCK_REALTIME ||
+            list_empty(&clock->abs_timer_list))
+                return ret;
+
+        do_posix_gettime(clock, &now);
+        delta.tv_sec = before.tv_sec - now.tv_sec;
+        delta.tv_nsec = before.tv_nsec - now.tv_nsec;
+        while (delta.tv_nsec >= NSEC_PER_SEC) {
+                delta.tv_sec ++;
+                delta.tv_nsec -= NSEC_PER_SEC;
+        }
+        while (delta.tv_nsec < 0) {
+                delta.tv_sec --;
+                delta.tv_nsec += NSEC_PER_SEC;
+        }
+
+        tstojiffie(&delta, clock->res, &exp);
+
+        spin_lock(&(clock->abs_timer_lock));
+        list_for_each_entry_safe(timer, tmp,
+                                 &clock->abs_timer_list,
+                                 abs_timer_entry) {
+                if (timer && del_timer(timer)) { //the timer has not
run
+                        timer->expires += exp; 
+                        add_timer(timer);
+                } else
+                        list_del(&timer->abs_timer_entry);
+        }
+        spin_unlock(&(clock->abs_timer_lock));
+        return ret;
 }
 
 asmlinkage long

Good Luck !
Boris Hu (Hu Jiangtao)
Intel China Software Center
86-021-5257-4545#1277
iNET: 8-752-1277
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Attachment: posix-abs_timer-bugfix.diff
Description: posix-abs_timer-bugfix.diff