From: Oleg Nesterov Date: Wed, 17 Oct 2007 06:27:22 +0000 (-0700) Subject: exec: simplify ->sighand switching X-Git-Tag: v2.6.24-rc1~675 X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=0840a90d943bcde2fbfeabd3c256236eed2273cd;p=linux.git exec: simplify ->sighand switching There is no any reason to do recalc_sigpending() after changing ->sighand. To begin with, recalc_sigpending() does not take ->sighand into account. This means we don't need to take newsighand->siglock while changing sighands. rcu_assign_pointer() provides a necessary barrier, and if another process reads the new ->sighand it should either take tasklist_lock or it should use lock_task_sighand() which has a corresponding smp_read_barrier_depends(). Signed-off-by: Oleg Nesterov Cc: Roland McGrath Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/fs/exec.c b/fs/exec.c index 59c0038baa4f..7f325df5e014 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -916,12 +916,7 @@ static int de_thread(struct task_struct *tsk) write_lock_irq(&tasklist_lock); spin_lock(&oldsighand->siglock); - spin_lock_nested(&newsighand->siglock, SINGLE_DEPTH_NESTING); - rcu_assign_pointer(tsk->sighand, newsighand); - recalc_sigpending(); - - spin_unlock(&newsighand->siglock); spin_unlock(&oldsighand->siglock); write_unlock_irq(&tasklist_lock); @@ -931,12 +926,11 @@ static int de_thread(struct task_struct *tsk) BUG_ON(!thread_group_leader(tsk)); return 0; } - + /* * These functions flushes out all traces of the currently running executable * so that a new one can be started */ - static void flush_old_files(struct files_struct * files) { long j = -1;