Home Home > GIT Browse
summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorOleg Nesterov <oleg@tv-sign.ru>2005-10-23 20:25:39 +0400
committerLinus Torvalds <torvalds@g5.osdl.org>2005-10-24 08:12:35 -0700
commit108150ea78003044e41150c75259447b2c0953b6 (patch)
treeffe0b7e59e6ca1c8a4dad18110e485e5c72872bc
parentba9e358fd04190a59e605c2963a15e014139a707 (diff)
[PATCH] posix-timers: fix cleanup_timers() and run_posix_cpu_timers() races
1. cleanup_timers() sets timer->task = NULL under tasklist + ->sighand locks. That means that this code in posix_cpu_timer_del() and posix_cpu_timer_set() lock_timer(timer); if (timer->task == NULL) return; read_lock(tasklist); put_task_struct(timer->task) is racy. With this patch timer->task modified and accounted only under timer->it_lock. Sadly, this means that dead task_struct won't be freed until timer deleted or armed. 2. run_posix_cpu_timers() collects expired timers into local list under tasklist + ->sighand again. That means that posix_cpu_timer_del() should check timer->it.cpu.firing under these locks too. Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--kernel/posix-cpu-timers.c29
1 files changed, 10 insertions, 19 deletions
diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index d30b304a3384..30ab39a27736 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -380,14 +380,9 @@ int posix_cpu_timer_create(struct k_itimer *new_timer)
int posix_cpu_timer_del(struct k_itimer *timer)
{
struct task_struct *p = timer->it.cpu.task;
+ int ret = 0;
- if (timer->it.cpu.firing)
- return TIMER_RETRY;
-
- if (unlikely(p == NULL))
- return 0;
-
- if (!list_empty(&timer->it.cpu.entry)) {
+ if (likely(p != NULL)) {
read_lock(&tasklist_lock);
if (unlikely(p->signal == NULL)) {
/*
@@ -396,18 +391,20 @@ int posix_cpu_timer_del(struct k_itimer *timer)
*/
BUG_ON(!list_empty(&timer->it.cpu.entry));
} else {
- /*
- * Take us off the task's timer list.
- */
spin_lock(&p->sighand->siglock);
- list_del(&timer->it.cpu.entry);
+ if (timer->it.cpu.firing)
+ ret = TIMER_RETRY;
+ else
+ list_del(&timer->it.cpu.entry);
spin_unlock(&p->sighand->siglock);
}
read_unlock(&tasklist_lock);
+
+ if (!ret)
+ put_task_struct(p);
}
- put_task_struct(p);
- return 0;
+ return ret;
}
/*
@@ -424,8 +421,6 @@ static void cleanup_timers(struct list_head *head,
cputime_t ptime = cputime_add(utime, stime);
list_for_each_entry_safe(timer, next, head, entry) {
- put_task_struct(timer->task);
- timer->task = NULL;
list_del_init(&timer->entry);
if (cputime_lt(timer->expires.cpu, ptime)) {
timer->expires.cpu = cputime_zero;
@@ -437,8 +432,6 @@ static void cleanup_timers(struct list_head *head,
++head;
list_for_each_entry_safe(timer, next, head, entry) {
- put_task_struct(timer->task);
- timer->task = NULL;
list_del_init(&timer->entry);
if (cputime_lt(timer->expires.cpu, utime)) {
timer->expires.cpu = cputime_zero;
@@ -450,8 +443,6 @@ static void cleanup_timers(struct list_head *head,
++head;
list_for_each_entry_safe(timer, next, head, entry) {
- put_task_struct(timer->task);
- timer->task = NULL;
list_del_init(&timer->entry);
if (timer->expires.sched < sched_time) {
timer->expires.sched = 0;