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exec: simplify ->sighand switching

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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 <oleg@tv-sign.ru>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Oleg Nesterov 2007-10-16 23:27:22 -07:00 committed by Linus Torvalds
parent 2b47c3611d
commit 0840a90d94
1 changed files with 1 additions and 7 deletions
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6
fs/exec.c
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@ -916,12 +916,7 @@ no_thread_group:
write_lock_irq(&tasklist_lock); write_lock_irq(&tasklist_lock);
spin_lock(&oldsighand->siglock); spin_lock(&oldsighand->siglock);
spin_lock_nested(&newsighand->siglock, SINGLE_DEPTH_NESTING);
rcu_assign_pointer(tsk->sighand, newsighand); rcu_assign_pointer(tsk->sighand, newsighand);
recalc_sigpending();
spin_unlock(&newsighand->siglock);
spin_unlock(&oldsighand->siglock); spin_unlock(&oldsighand->siglock);
write_unlock_irq(&tasklist_lock); write_unlock_irq(&tasklist_lock);
@ -936,7 +931,6 @@ no_thread_group:
* These functions flushes out all traces of the currently running executable * These functions flushes out all traces of the currently running executable
* so that a new one can be started * so that a new one can be started
*/ */
static void flush_old_files(struct files_struct * files) static void flush_old_files(struct files_struct * files)
{ {
long j = -1; long j = -1;