From: Oleg Nesterov 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 --- fs/exec.c | 8 +------- 1 file changed, 1 insertion(+), 7 deletions(-) diff -puN fs/exec.c~exec-simplify-sighand-switching fs/exec.c --- a/fs/exec.c~exec-simplify-sighand-switching +++ a/fs/exec.c @@ -919,12 +919,7 @@ no_thread_group: 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); @@ -934,12 +929,11 @@ no_thread_group: 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; _