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authorIngo Molnar <mingo@kernel.org>2014-12-12 09:09:03 +0100
committerIngo Molnar <mingo@kernel.org>2014-12-12 09:09:03 +0100
commit3459f0d78ffe27a1b341c22eb158b622eaaea3fc (patch)
tree715b0575eec541d0181876ad367ca5480cdcecf3 /kernel/signal.c
parent9fc81d87420d0d3fd62d5e5529972c0ad9eab9cc (diff)
parentbee2782f30f66898be3f74ad02e4d1f87a969694 (diff)
Merge branch 'linus' into perf/urgent, to pick up the upstream merged bits
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/signal.c')
-rw-r--r--kernel/signal.c42
1 files changed, 25 insertions, 17 deletions
diff --git a/kernel/signal.c b/kernel/signal.c
index 8f0876f9f6d..19e35135fc6 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1275,7 +1275,17 @@ struct sighand_struct *__lock_task_sighand(struct task_struct *tsk,
local_irq_restore(*flags);
break;
}
-
+ /*
+ * This sighand can be already freed and even reused, but
+ * we rely on SLAB_DESTROY_BY_RCU and sighand_ctor() which
+ * initializes ->siglock: this slab can't go away, it has
+ * the same object type, ->siglock can't be reinitialized.
+ *
+ * We need to ensure that tsk->sighand is still the same
+ * after we take the lock, we can race with de_thread() or
+ * __exit_signal(). In the latter case the next iteration
+ * must see ->sighand == NULL.
+ */
spin_lock(&sighand->siglock);
if (likely(sighand == tsk->sighand)) {
rcu_read_unlock();
@@ -1331,23 +1341,21 @@ int kill_pid_info(int sig, struct siginfo *info, struct pid *pid)
int error = -ESRCH;
struct task_struct *p;
- rcu_read_lock();
-retry:
- p = pid_task(pid, PIDTYPE_PID);
- if (p) {
- error = group_send_sig_info(sig, info, p);
- if (unlikely(error == -ESRCH))
- /*
- * The task was unhashed in between, try again.
- * If it is dead, pid_task() will return NULL,
- * if we race with de_thread() it will find the
- * new leader.
- */
- goto retry;
- }
- rcu_read_unlock();
+ for (;;) {
+ rcu_read_lock();
+ p = pid_task(pid, PIDTYPE_PID);
+ if (p)
+ error = group_send_sig_info(sig, info, p);
+ rcu_read_unlock();
+ if (likely(!p || error != -ESRCH))
+ return error;
- return error;
+ /*
+ * The task was unhashed in between, try again. If it
+ * is dead, pid_task() will return NULL, if we race with
+ * de_thread() it will find the new leader.
+ */
+ }
}
int kill_proc_info(int sig, struct siginfo *info, pid_t pid)