signalfd: make it group-wide, fix posix-timers scheduling

f9ee228b · Oleg Nesterov <[email protected]> · 2007-08-22 14:01:48 -07:00

With this patch any thread can dequeue its own private signals via signalfd,
even if it was created by another sub-thread.

To do so, we pass "current" to dequeue_signal() if the caller is from the same
thread group. This also fixes the scheduling of posix timers broken by the
previous patch.

If the caller doesn't belong to this thread group, we can't handle __SI_TIMER
case properly anyway. Perhaps we should forbid the cross-process signalfd usage
and convert ctx->tsk to ctx->sighand.

Signed-off-by: Oleg Nesterov <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Davide Libenzi <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Michael Kerrisk <[email protected]>
Cc: Roland McGrath <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Commit: f9ee228bdc82cff8ea1ec00fd952890e00679dd8
Parents: 834d216e

Changes

2 files changed · +12 −11

File	Status	Add	Del	Content
fs/exec.c	modified	+2	−7	View file
fs/signalfd.c	modified	+10	−4	View file

fs/exec.c

View file

diff --git a/fs/exec.c b/fs/exec.c
index ce62f7b..af4361c 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -780,18 +780,12 @@ static int de_thread(struct task_struct *tsk)
 	int count;
 
 	/*
-	 * Tell all the sighand listeners that this sighand has
-	 * been detached. The signalfd_detach() function grabs the
-	 * sighand lock, if signal listeners are present on the sighand.
-	 */
-	signalfd_detach(tsk);
-
-	/*
 	 * If we don't share sighandlers, then we aren't sharing anything
 	 * and we can just re-use it all.
 	 */
 	if (atomic_read(&oldsighand->count) <= 1) {
 		BUG_ON(atomic_read(&sig->count) != 1);
+		signalfd_detach(tsk);
 		exit_itimers(sig);
 		return 0;
 	}
@@ -930,6 +924,7 @@ static int de_thread(struct task_struct *tsk)
 	sig->flags = 0;
 
 no_thread_group:
+	signalfd_detach(tsk);
 	exit_itimers(sig);
 	if (leader)
 		release_task(leader);

fs/signalfd.c

View file

diff --git a/fs/signalfd.c b/fs/signalfd.c
index 7b941ab..a8e293d 100644
--- a/fs/signalfd.c
+++ b/fs/signalfd.c
@@ -56,12 +56,18 @@ static int signalfd_lock(struct signalfd_ctx *ctx, struct signalfd_lockctx *lk)
 		sighand = lock_task_sighand(lk->tsk, &lk->flags);
 	rcu_read_unlock();
 
-	if (sighand && !ctx->tsk) {
+	if (!sighand)
+		return 0;
+
+	if (!ctx->tsk) {
 		unlock_task_sighand(lk->tsk, &lk->flags);
-		sighand = NULL;
+		return 0;
 	}
 
-	return sighand != NULL;
+	if (lk->tsk->tgid == current->tgid)
+		lk->tsk = current;
+
+	return 1;
 }
 
 static void signalfd_unlock(struct signalfd_lockctx *lk)
@@ -331,7 +337,7 @@ asmlinkage long sys_signalfd(int ufd, sigset_t __user *user_mask, size_t sizemas
 
 		init_waitqueue_head(&ctx->wqh);
 		ctx->sigmask = sigmask;
-		ctx->tsk = current;
+		ctx->tsk = current->group_leader;
 
 		sighand = current->sighand;
 		/*