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ptrace: simplify ptrace_stop()->sigkill_pending() path

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1. SIGKILL can't be blocked, remove this check from sigkill_pending().

2. When ptrace_stop() sees sigkill_pending() == T, it can just return.
   Kill "int killed" and simplify the code. This also is more correct,
   the tracer shouldn't see us in TASK_TRACED if we are not going to
   stop.

I strongly believe this code needs further changes.  We should do the "was
this task killed" check unconditionally, currently it depends on
arch_ptrace_stop_needed().  On the other hand, sigkill_pending() isn't
very clever.  If the task was killed tkill(SIGKILL), the signal can be
already dequeued if the caller is do_exit().

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 2008-07-25 01:47:37 -07:00 committed by Linus Torvalds
parent 364d3c13c1
commit 3d749b9e67
1 changed files with 5 additions and 7 deletions
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12
kernel/signal.c
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@ -1496,9 +1496,8 @@ static inline int may_ptrace_stop(void)
*/
static int sigkill_pending(struct task_struct *tsk)
{
return ((sigismember(&tsk->pending.signal, SIGKILL) ||
sigismember(&tsk->signal->shared_pending.signal, SIGKILL)) &&
!unlikely(sigismember(&tsk->blocked, SIGKILL)));
return sigismember(&tsk->pending.signal, SIGKILL) ||
sigismember(&tsk->signal->shared_pending.signal, SIGKILL);
}
/*
@ -1514,8 +1513,6 @@ static int sigkill_pending(struct task_struct *tsk)
*/
static void ptrace_stop(int exit_code, int clear_code, siginfo_t *info)
{
int killed = 0;
if (arch_ptrace_stop_needed(exit_code, info)) {
/*
* The arch code has something special to do before a
@ -1531,7 +1528,8 @@ static void ptrace_stop(int exit_code, int clear_code, siginfo_t *info)
spin_unlock_irq(&current->sighand->siglock);
arch_ptrace_stop(exit_code, info);
spin_lock_irq(&current->sighand->siglock);
killed = sigkill_pending(current);
if (sigkill_pending(current))
return;
}
/*
@ -1548,7 +1546,7 @@ static void ptrace_stop(int exit_code, int clear_code, siginfo_t *info)
__set_current_state(TASK_TRACED);
spin_unlock_irq(&current->sighand->siglock);
read_lock(&tasklist_lock);
if (!unlikely(killed) && may_ptrace_stop()) {
if (may_ptrace_stop()) {
do_notify_parent_cldstop(current, CLD_TRAPPED);
read_unlock(&tasklist_lock);
schedule();