From 6b3934ef52712ece50605dfc72e55d00c580831a Mon Sep 17 00:00:00 2001 From: Oleg Nesterov 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 Cc: "Eric W. Biederman" Acked-by: David Howells Signed-off-by: Adrian Bunk Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- 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 69c2a1e1529..7dd430b697a 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 15e1d9736b1..3af03b19c98 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 8a46ad52be8..0aff28cdbad 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 1d7f4463c32..54e9ef673e6 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. */ -- 2.20.1