diff options
author | Oleg Nesterov <oleg@redhat.com> | 2010-05-26 21:43:16 (GMT) |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-05-27 16:12:46 (GMT) |
commit | ea6d290ca34c4fd91b7348338c0cc7bdeff94a35 (patch) | |
tree | 6e9bd367650d9233c5b6cf1059845f17cb1bc460 /kernel/exit.c | |
parent | 4dec2a91fd7e8815d730afbfdcf085cbf53433ac (diff) | |
download | linux-fsl-qoriq-ea6d290ca34c4fd91b7348338c0cc7bdeff94a35.tar.xz |
signals: make task_struct->signal immutable/refcountable
We have a lot of problems with accessing task_struct->signal, it can
"disappear" at any moment. Even current can't use its ->signal safely
after exit_notify(). ->siglock helps, but it is not convenient, not
always possible, and sometimes it makes sense to use task->signal even
after this task has already dead.
This patch adds the reference counter, sigcnt, into signal_struct. This
reference is owned by task_struct and it is dropped in
__put_task_struct(). Perhaps it makes sense to export
get/put_signal_struct() later, but currently I don't see the immediate
reason.
Rename __cleanup_signal() to free_signal_struct() and unexport it. With
the previous changes it does nothing except kmem_cache_free().
Change __exit_signal() to not clear/free ->signal, it will be freed when
the last reference to any thread in the thread group goes away.
Note:
- when the last thead exits signal->tty can point to nowhere, see
the next patch.
- with or without this patch signal_struct->count should go away,
or at least it should be "int nr_threads" for fs/proc. This will
be addressed later.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Alan Cox <alan@linux.intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <peterz@infradead.org>
Acked-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/exit.c')
-rw-r--r-- | kernel/exit.c | 3 |
1 files changed, 0 insertions, 3 deletions
diff --git a/kernel/exit.c b/kernel/exit.c index 4a72f17..92af5cd 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -134,8 +134,6 @@ static void __exit_signal(struct task_struct *tsk) * doing sigqueue_free() if we have SIGQUEUE_PREALLOC signals. */ flush_sigqueue(&tsk->pending); - - tsk->signal = NULL; tsk->sighand = NULL; spin_unlock(&sighand->siglock); @@ -150,7 +148,6 @@ static void __exit_signal(struct task_struct *tsk) */ task_rq_unlock_wait(tsk); tty_kref_put(sig->tty); - __cleanup_signal(sig); } } |