From 6b3934ef52712ece50605dfc72e55d00c580831a Mon Sep 17 00:00:00 2001
From: Oleg Nesterov <oleg@tv-sign.ru>
Date: Tue, 28 Mar 2006 16:11:16 -0800
Subject: [PATCH] [PATCH] copy_process: cleanup bad_fork_cleanup_signal
__exit_signal() does important cleanups atomically under ->siglock. It is
also called from copy_process's error path. This is not good, for example we
can't move __unhash_process() under ->siglock for that reason.
We should not mix these 2 paths, just look at ugly 'if (p->sighand)' under
'bad_fork_cleanup_sighand:' label. For copy_process() case it is sufficient
to just backout copy_signal(), nothing more.
Again, nobody can see this task yet. For CLONE_THREAD case we just decrement
signal->count, otherwise nobody can see this ->signal and we can free it
lockless.
This patch assumes it is safe to do exit_thread_group_keys() without
tasklist_lock.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---
include/linux/sched.h | 2 +-
include/linux/slab.h | 1 -
kernel/fork.c | 23 +++++++++++++++++++----
kernel/signal.c | 15 +--------------
4 files changed, 21 insertions(+), 20 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 69c2a1e1529e..7dd430b697aa 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1149,7 +1149,7 @@ extern void flush_thread(void);
extern void exit_thread(void);
extern void exit_files(struct task_struct *);
-extern void exit_signal(struct task_struct *);
+extern void __cleanup_signal(struct signal_struct *);
extern void __exit_signal(struct task_struct *);
extern void __exit_sighand(struct task_struct *);
extern void exit_itimers(struct signal_struct *);
diff --git a/include/linux/slab.h b/include/linux/slab.h
index 15e1d9736b1b..3af03b19c983 100644
--- a/include/linux/slab.h
+++ b/include/linux/slab.h
@@ -210,7 +210,6 @@ extern kmem_cache_t *names_cachep;
extern kmem_cache_t *files_cachep;
extern kmem_cache_t *filp_cachep;
extern kmem_cache_t *fs_cachep;
-extern kmem_cache_t *signal_cachep;
extern kmem_cache_t *sighand_cachep;
extern kmem_cache_t *bio_cachep;
diff --git a/kernel/fork.c b/kernel/fork.c
index 8a46ad52be8f..0aff28cdbadd 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -84,7 +84,7 @@ static kmem_cache_t *task_struct_cachep;
#endif
/* SLAB cache for signal_struct structures (tsk->signal) */
-kmem_cache_t *signal_cachep;
+static kmem_cache_t *signal_cachep;
/* SLAB cache for sighand_struct structures (tsk->sighand) */
kmem_cache_t *sighand_cachep;
@@ -872,6 +872,22 @@ static inline int copy_signal(unsigned long clone_flags, struct task_struct * ts
return 0;
}
+void __cleanup_signal(struct signal_struct *sig)
+{
+ exit_thread_group_keys(sig);
+ kmem_cache_free(signal_cachep, sig);
+}
+
+static inline void cleanup_signal(struct task_struct *tsk)
+{
+ struct signal_struct *sig = tsk->signal;
+
+ atomic_dec(&sig->live);
+
+ if (atomic_dec_and_test(&sig->count))
+ __cleanup_signal(sig);
+}
+
static inline void copy_flags(unsigned long clone_flags, struct task_struct *p)
{
unsigned long new_flags = p->flags;
@@ -1206,10 +1222,9 @@ bad_fork_cleanup_mm:
if (p->mm)
mmput(p->mm);
bad_fork_cleanup_signal:
- exit_signal(p);
+ cleanup_signal(p);
bad_fork_cleanup_sighand:
- if (p->sighand)
- __exit_sighand(p);
+ __exit_sighand(p);
bad_fork_cleanup_fs:
exit_fs(p); /* blocking */
bad_fork_cleanup_files:
diff --git a/kernel/signal.c b/kernel/signal.c
index 1d7f4463c32d..54e9ef673e68 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -395,23 +395,10 @@ void __exit_signal(struct task_struct *tsk)
clear_tsk_thread_flag(tsk,TIF_SIGPENDING);
flush_sigqueue(&tsk->pending);
if (sig) {
- /*
- * We are cleaning up the signal_struct here.
- */
- exit_thread_group_keys(sig);
- kmem_cache_free(signal_cachep, sig);
+ __cleanup_signal(sig);
}
}
-void exit_signal(struct task_struct *tsk)
-{
- atomic_dec(&tsk->signal->live);
-
- write_lock_irq(&tasklist_lock);
- __exit_signal(tsk);
- write_unlock_irq(&tasklist_lock);
-}
-
/*
* Flush all handlers for a task.
*/
--
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