Hello!
Additional RCU signal fixes to cover a race with exec() and to add
some rcu_dereference()s from earlier patches.
Signed-off-by: <[email protected]>
---
signal.c | 28 +++++++++++++++-------------
1 files changed, 15 insertions(+), 13 deletions(-)
diff -urpNa -X dontdiff linux-2.6.14-mm0/kernel/signal.c linux-2.6.14-mm0-fix/kernel/signal.c
--- linux-2.6.14-mm0/kernel/signal.c 2005-11-04 14:37:18.000000000 -0800
+++ linux-2.6.14-mm0-fix/kernel/signal.c 2005-11-04 17:23:40.000000000 -0800
@@ -337,7 +337,7 @@ void exit_sighand(struct task_struct *ts
write_lock_irq(&tasklist_lock);
rcu_read_lock();
if (tsk->sighand != NULL) {
- struct sighand_struct *sighand = tsk->sighand;
+ struct sighand_struct *sighand = rcu_dereference(tsk->sighand);
spin_lock(&sighand->siglock);
__exit_sighand(tsk);
spin_unlock(&sighand->siglock);
@@ -352,13 +352,14 @@ void exit_sighand(struct task_struct *ts
void __exit_signal(struct task_struct *tsk)
{
struct signal_struct * sig = tsk->signal;
- struct sighand_struct * sighand = tsk->sighand;
+ struct sighand_struct * sighand;
if (!sig)
BUG();
if (!atomic_read(&sig->count))
BUG();
rcu_read_lock();
+ sighand = rcu_dereference(tsk->sighand);
spin_lock(&sighand->siglock);
posix_cpu_timers_exit(tsk);
if (atomic_dec_and_test(&sig->count)) {
@@ -1100,7 +1101,7 @@ void zap_other_threads(struct task_struc
}
/*
- * Must be called with the tasklist_lock held for reading!
+ * Must be called under rcu_read_lock() or with tasklist_lock read-held.
*/
int group_send_sig_info(int sig, struct siginfo *info, struct task_struct *p)
{
@@ -1386,7 +1387,7 @@ send_sigqueue(int sig, struct sigqueue *
{
unsigned long flags;
int ret = 0;
- struct sighand_struct *sh = p->sighand;
+ struct sighand_struct *sh;
BUG_ON(!(q->flags & SIGQUEUE_PREALLOC));
@@ -1405,7 +1406,15 @@ send_sigqueue(int sig, struct sigqueue *
goto out_err;
}
+retry:
+ sh = rcu_dereference(p->sighand);
+
spin_lock_irqsave(&sh->siglock, flags);
+ if (p->sighand != sh) {
+ /* We raced with exec() in a multithreaded process... */
+ spin_unlock_irqrestore(&sh->siglock, flags);
+ goto retry;
+ }
/*
* We do the check here again to handle the following scenario:
@@ -1464,15 +1473,8 @@ send_group_sigqueue(int sig, struct sigq
BUG_ON(!(q->flags & SIGQUEUE_PREALLOC));
- while (!read_trylock(&tasklist_lock)) {
- if (!p->sighand)
- return -1;
- cpu_relax();
- }
- if (unlikely(!p->sighand)) {
- ret = -1;
- goto out_err;
- }
+ read_lock(&tasklist_lock);
+ /* Since it_lock is held, p->sighand cannot be NULL. */
spin_lock_irqsave(&p->sighand->siglock, flags);
handle_stop_signal(sig, p);
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
