static int recalc_sigpending_tsk(struct task_struct *t)
{
- if (t->signal->group_stop_count > 0 ||
+ if ((t->group_stop & GROUP_STOP_PENDING) ||
PENDING(&t->pending, &t->blocked) ||
PENDING(&t->signal->shared_pending, &t->blocked)) {
set_tsk_thread_flag(t, TIF_SIGPENDING);
current->comm, current->pid, sig);
}
+/**
+ * task_clear_group_stop_trapping - clear group stop trapping bit
+ * @task: target task
+ *
+ * If GROUP_STOP_TRAPPING is set, a ptracer is waiting for us. Clear it
+ * and wake up the ptracer. Note that we don't need any further locking.
+ * @task->siglock guarantees that @task->parent points to the ptracer.
+ *
+ * CONTEXT:
+ * Must be called with @task->sighand->siglock held.
+ */
+static void task_clear_group_stop_trapping(struct task_struct *task)
+{
+ if (unlikely(task->group_stop & GROUP_STOP_TRAPPING)) {
+ task->group_stop &= ~GROUP_STOP_TRAPPING;
+ __wake_up_sync(&task->parent->signal->wait_chldexit,
+ TASK_UNINTERRUPTIBLE, 1);
+ }
+}
+
+/**
+ * task_clear_group_stop_pending - clear pending group stop
+ * @task: target task
+ *
+ * Clear group stop states for @task.
+ *
+ * CONTEXT:
+ * Must be called with @task->sighand->siglock held.
+ */
+void task_clear_group_stop_pending(struct task_struct *task)
+{
+ task->group_stop &= ~(GROUP_STOP_PENDING | GROUP_STOP_CONSUME |
+ GROUP_STOP_DEQUEUED);
+}
+
+/**
+ * task_participate_group_stop - participate in a group stop
+ * @task: task participating in a group stop
+ *
+ * @task has GROUP_STOP_PENDING set and is participating in a group stop.
+ * Group stop states are cleared and the group stop count is consumed if
+ * %GROUP_STOP_CONSUME was set. If the consumption completes the group
+ * stop, the appropriate %SIGNAL_* flags are set.
+ *
+ * CONTEXT:
+ * Must be called with @task->sighand->siglock held.
+ *
+ * RETURNS:
+ * %true if group stop completion should be notified to the parent, %false
+ * otherwise.
+ */
+static bool task_participate_group_stop(struct task_struct *task)
+{
+ struct signal_struct *sig = task->signal;
+ bool consume = task->group_stop & GROUP_STOP_CONSUME;
+
+ WARN_ON_ONCE(!(task->group_stop & GROUP_STOP_PENDING));
+
+ task_clear_group_stop_pending(task);
+
+ if (!consume)
+ return false;
+
+ if (!WARN_ON_ONCE(sig->group_stop_count == 0))
+ sig->group_stop_count--;
+
+ /*
+ * Tell the caller to notify completion iff we are entering into a
+ * fresh group stop. Read comment in do_signal_stop() for details.
+ */
+ if (!sig->group_stop_count && !(sig->flags & SIGNAL_STOP_STOPPED)) {
+ sig->flags = SIGNAL_STOP_STOPPED;
+ return true;
+ }
+ return false;
+}
+
/*
* allocate a new signal queue record
* - this may be called without locks if and only if t == current, otherwise an
* is to alert stop-signal processing code when another
* processor has come along and cleared the flag.
*/
- tsk->signal->flags |= SIGNAL_STOP_DEQUEUED;
+ current->group_stop |= GROUP_STOP_DEQUEUED;
}
if ((info->si_code & __SI_MASK) == __SI_TIMER && info->si_sys_private) {
/*
} else if (sig == SIGCONT) {
unsigned int why;
/*
- * Remove all stop signals from all queues,
- * and wake all threads.
+ * Remove all stop signals from all queues, wake all threads.
*/
rm_from_queue(SIG_KERNEL_STOP_MASK, &signal->shared_pending);
t = p;
do {
- unsigned int state;
+ task_clear_group_stop_pending(t);
rm_from_queue(SIG_KERNEL_STOP_MASK, &t->pending);
- /*
- * If there is a handler for SIGCONT, we must make
- * sure that no thread returns to user mode before
- * we post the signal, in case it was the only
- * thread eligible to run the signal handler--then
- * it must not do anything between resuming and
- * running the handler. With the TIF_SIGPENDING
- * flag set, the thread will pause and acquire the
- * siglock that we hold now and until we've queued
- * the pending signal.
- *
- * Wake up the stopped thread _after_ setting
- * TIF_SIGPENDING
- */
- state = __TASK_STOPPED;
- if (sig_user_defined(t, SIGCONT) && !sigismember(&t->blocked, SIGCONT)) {
- set_tsk_thread_flag(t, TIF_SIGPENDING);
- state |= TASK_INTERRUPTIBLE;
- }
- wake_up_state(t, state);
+ wake_up_state(t, __TASK_STOPPED);
} while_each_thread(p, t);
/*
signal->flags = why | SIGNAL_STOP_CONTINUED;
signal->group_stop_count = 0;
signal->group_exit_code = 0;
- } else {
- /*
- * We are not stopped, but there could be a stop
- * signal in the middle of being processed after
- * being removed from the queue. Clear that too.
- */
- signal->flags &= ~SIGNAL_STOP_DEQUEUED;
}
}
signal->group_stop_count = 0;
t = p;
do {
+ task_clear_group_stop_pending(t);
sigaddset(&t->pending.signal, SIGKILL);
signal_wake_up(t, 1);
} while_each_thread(p, t);
p->signal->group_stop_count = 0;
while_each_thread(p, t) {
+ task_clear_group_stop_pending(t);
count++;
/* Don't bother with already dead threads */
return ret;
}
-static void do_notify_parent_cldstop(struct task_struct *tsk, int why)
+/**
+ * do_notify_parent_cldstop - notify parent of stopped/continued state change
+ * @tsk: task reporting the state change
+ * @for_ptracer: the notification is for ptracer
+ * @why: CLD_{CONTINUED|STOPPED|TRAPPED} to report
+ *
+ * Notify @tsk's parent that the stopped/continued state has changed. If
+ * @for_ptracer is %false, @tsk's group leader notifies to its real parent.
+ * If %true, @tsk reports to @tsk->parent which should be the ptracer.
+ *
+ * CONTEXT:
+ * Must be called with tasklist_lock at least read locked.
+ */
+static void do_notify_parent_cldstop(struct task_struct *tsk,
+ bool for_ptracer, int why)
{
struct siginfo info;
unsigned long flags;
struct task_struct *parent;
struct sighand_struct *sighand;
- if (task_ptrace(tsk))
+ if (for_ptracer) {
parent = tsk->parent;
- else {
+ } else {
tsk = tsk->group_leader;
parent = tsk->real_parent;
}
sigismember(&tsk->signal->shared_pending.signal, SIGKILL);
}
+/*
+ * Test whether the target task of the usual cldstop notification - the
+ * real_parent of @child - is in the same group as the ptracer.
+ */
+static bool real_parent_is_ptracer(struct task_struct *child)
+{
+ return same_thread_group(child->parent, child->real_parent);
+}
+
/*
* This must be called with current->sighand->siglock held.
*
* If we actually decide not to stop at all because the tracer
* is gone, we keep current->exit_code unless clear_code.
*/
-static void ptrace_stop(int exit_code, int clear_code, siginfo_t *info)
+static void ptrace_stop(int exit_code, int why, int clear_code, siginfo_t *info)
__releases(¤t->sighand->siglock)
__acquires(¤t->sighand->siglock)
{
+ bool gstop_done = false;
+
if (arch_ptrace_stop_needed(exit_code, info)) {
/*
* The arch code has something special to do before a
}
/*
- * If there is a group stop in progress,
- * we must participate in the bookkeeping.
+ * If @why is CLD_STOPPED, we're trapping to participate in a group
+ * stop. Do the bookkeeping. Note that if SIGCONT was delievered
+ * while siglock was released for the arch hook, PENDING could be
+ * clear now. We act as if SIGCONT is received after TASK_TRACED
+ * is entered - ignore it.
*/
- if (current->signal->group_stop_count > 0)
- --current->signal->group_stop_count;
+ if (why == CLD_STOPPED && (current->group_stop & GROUP_STOP_PENDING))
+ gstop_done = task_participate_group_stop(current);
current->last_siginfo = info;
current->exit_code = exit_code;
- /* Let the debugger run. */
- __set_current_state(TASK_TRACED);
+ /*
+ * TRACED should be visible before TRAPPING is cleared; otherwise,
+ * the tracer might fail do_wait().
+ */
+ set_current_state(TASK_TRACED);
+
+ /*
+ * We're committing to trapping. Clearing GROUP_STOP_TRAPPING and
+ * transition to TASK_TRACED should be atomic with respect to
+ * siglock. This hsould be done after the arch hook as siglock is
+ * released and regrabbed across it.
+ */
+ task_clear_group_stop_trapping(current);
+
spin_unlock_irq(¤t->sighand->siglock);
read_lock(&tasklist_lock);
if (may_ptrace_stop()) {
- do_notify_parent_cldstop(current, CLD_TRAPPED);
+ /*
+ * Notify parents of the stop.
+ *
+ * While ptraced, there are two parents - the ptracer and
+ * the real_parent of the group_leader. The ptracer should
+ * know about every stop while the real parent is only
+ * interested in the completion of group stop. The states
+ * for the two don't interact with each other. Notify
+ * separately unless they're gonna be duplicates.
+ */
+ do_notify_parent_cldstop(current, true, why);
+ if (gstop_done && !real_parent_is_ptracer(current))
+ do_notify_parent_cldstop(current, false, why);
+
/*
* Don't want to allow preemption here, because
* sys_ptrace() needs this task to be inactive.
/*
* By the time we got the lock, our tracer went away.
* Don't drop the lock yet, another tracer may come.
+ *
+ * If @gstop_done, the ptracer went away between group stop
+ * completion and here. During detach, it would have set
+ * GROUP_STOP_PENDING on us and we'll re-enter TASK_STOPPED
+ * in do_signal_stop() on return, so notifying the real
+ * parent of the group stop completion is enough.
*/
+ if (gstop_done)
+ do_notify_parent_cldstop(current, false, why);
+
__set_current_state(TASK_RUNNING);
if (clear_code)
current->exit_code = 0;
/* Let the debugger run. */
spin_lock_irq(¤t->sighand->siglock);
- ptrace_stop(exit_code, 1, &info);
+ ptrace_stop(exit_code, CLD_TRAPPED, 1, &info);
spin_unlock_irq(¤t->sighand->siglock);
}
static int do_signal_stop(int signr)
{
struct signal_struct *sig = current->signal;
- int notify;
- if (!sig->group_stop_count) {
+ if (!(current->group_stop & GROUP_STOP_PENDING)) {
+ unsigned int gstop = GROUP_STOP_PENDING | GROUP_STOP_CONSUME;
struct task_struct *t;
- if (!likely(sig->flags & SIGNAL_STOP_DEQUEUED) ||
+ /* signr will be recorded in task->group_stop for retries */
+ WARN_ON_ONCE(signr & ~GROUP_STOP_SIGMASK);
+
+ if (!likely(current->group_stop & GROUP_STOP_DEQUEUED) ||
unlikely(signal_group_exit(sig)))
return 0;
/*
- * There is no group stop already in progress.
- * We must initiate one now.
+ * There is no group stop already in progress. We must
+ * initiate one now.
+ *
+ * While ptraced, a task may be resumed while group stop is
+ * still in effect and then receive a stop signal and
+ * initiate another group stop. This deviates from the
+ * usual behavior as two consecutive stop signals can't
+ * cause two group stops when !ptraced. That is why we
+ * also check !task_is_stopped(t) below.
+ *
+ * The condition can be distinguished by testing whether
+ * SIGNAL_STOP_STOPPED is already set. Don't generate
+ * group_exit_code in such case.
+ *
+ * This is not necessary for SIGNAL_STOP_CONTINUED because
+ * an intervening stop signal is required to cause two
+ * continued events regardless of ptrace.
*/
- sig->group_exit_code = signr;
+ if (!(sig->flags & SIGNAL_STOP_STOPPED))
+ sig->group_exit_code = signr;
+ else
+ WARN_ON_ONCE(!task_ptrace(current));
+ current->group_stop &= ~GROUP_STOP_SIGMASK;
+ current->group_stop |= signr | gstop;
sig->group_stop_count = 1;
- for (t = next_thread(current); t != current; t = next_thread(t))
+ for (t = next_thread(current); t != current;
+ t = next_thread(t)) {
+ t->group_stop &= ~GROUP_STOP_SIGMASK;
/*
* Setting state to TASK_STOPPED for a group
* stop is always done with the siglock held,
* so this check has no races.
*/
- if (!(t->flags & PF_EXITING) &&
- !task_is_stopped_or_traced(t)) {
+ if (!(t->flags & PF_EXITING) && !task_is_stopped(t)) {
+ t->group_stop |= signr | gstop;
sig->group_stop_count++;
signal_wake_up(t, 0);
}
+ }
}
- /*
- * If there are no other threads in the group, or if there is
- * a group stop in progress and we are the last to stop, report
- * to the parent. When ptraced, every thread reports itself.
- */
- notify = sig->group_stop_count == 1 ? CLD_STOPPED : 0;
- notify = tracehook_notify_jctl(notify, CLD_STOPPED);
- /*
- * tracehook_notify_jctl() can drop and reacquire siglock, so
- * we keep ->group_stop_count != 0 before the call. If SIGCONT
- * or SIGKILL comes in between ->group_stop_count == 0.
- */
- if (sig->group_stop_count) {
- if (!--sig->group_stop_count)
- sig->flags = SIGNAL_STOP_STOPPED;
- current->exit_code = sig->group_exit_code;
+retry:
+ if (likely(!task_ptrace(current))) {
+ int notify = 0;
+
+ /*
+ * If there are no other threads in the group, or if there
+ * is a group stop in progress and we are the last to stop,
+ * report to the parent.
+ */
+ if (task_participate_group_stop(current))
+ notify = CLD_STOPPED;
+
__set_current_state(TASK_STOPPED);
+ spin_unlock_irq(¤t->sighand->siglock);
+
+ /*
+ * Notify the parent of the group stop completion. Because
+ * we're not holding either the siglock or tasklist_lock
+ * here, ptracer may attach inbetween; however, this is for
+ * group stop and should always be delivered to the real
+ * parent of the group leader. The new ptracer will get
+ * its notification when this task transitions into
+ * TASK_TRACED.
+ */
+ if (notify) {
+ read_lock(&tasklist_lock);
+ do_notify_parent_cldstop(current, false, notify);
+ read_unlock(&tasklist_lock);
+ }
+
+ /* Now we don't run again until woken by SIGCONT or SIGKILL */
+ schedule();
+
+ spin_lock_irq(¤t->sighand->siglock);
+ } else {
+ ptrace_stop(current->group_stop & GROUP_STOP_SIGMASK,
+ CLD_STOPPED, 0, NULL);
+ current->exit_code = 0;
}
- spin_unlock_irq(¤t->sighand->siglock);
- if (notify) {
- read_lock(&tasklist_lock);
- do_notify_parent_cldstop(current, notify);
- read_unlock(&tasklist_lock);
+ /*
+ * GROUP_STOP_PENDING could be set if another group stop has
+ * started since being woken up or ptrace wants us to transit
+ * between TASK_STOPPED and TRACED. Retry group stop.
+ */
+ if (current->group_stop & GROUP_STOP_PENDING) {
+ WARN_ON_ONCE(!(current->group_stop & GROUP_STOP_SIGMASK));
+ goto retry;
}
- /* Now we don't run again until woken by SIGCONT or SIGKILL */
- do {
- schedule();
- } while (try_to_freeze());
+ /* PTRACE_ATTACH might have raced with task killing, clear trapping */
+ task_clear_group_stop_trapping(current);
+
+ spin_unlock_irq(¤t->sighand->siglock);
tracehook_finish_jctl();
- current->exit_code = 0;
return 1;
}
ptrace_signal_deliver(regs, cookie);
/* Let the debugger run. */
- ptrace_stop(signr, 0, info);
+ ptrace_stop(signr, CLD_TRAPPED, 0, info);
/* We're back. Did the debugger cancel the sig? */
signr = current->exit_code;
* the CLD_ si_code into SIGNAL_CLD_MASK bits.
*/
if (unlikely(signal->flags & SIGNAL_CLD_MASK)) {
- int why = (signal->flags & SIGNAL_STOP_CONTINUED)
- ? CLD_CONTINUED : CLD_STOPPED;
+ struct task_struct *leader;
+ int why;
+
+ if (signal->flags & SIGNAL_CLD_CONTINUED)
+ why = CLD_CONTINUED;
+ else
+ why = CLD_STOPPED;
+
signal->flags &= ~SIGNAL_CLD_MASK;
- why = tracehook_notify_jctl(why, CLD_CONTINUED);
spin_unlock_irq(&sighand->siglock);
- if (why) {
- read_lock(&tasklist_lock);
- do_notify_parent_cldstop(current->group_leader, why);
- read_unlock(&tasklist_lock);
- }
+ /*
+ * Notify the parent that we're continuing. This event is
+ * always per-process and doesn't make whole lot of sense
+ * for ptracers, who shouldn't consume the state via
+ * wait(2) either, but, for backward compatibility, notify
+ * the ptracer of the group leader too unless it's gonna be
+ * a duplicate.
+ */
+ read_lock(&tasklist_lock);
+
+ do_notify_parent_cldstop(current, false, why);
+
+ leader = current->group_leader;
+ if (task_ptrace(leader) && !real_parent_is_ptracer(leader))
+ do_notify_parent_cldstop(leader, true, why);
+
+ read_unlock(&tasklist_lock);
+
goto relock;
}
if (unlikely(signr != 0))
ka = return_ka;
else {
- if (unlikely(signal->group_stop_count > 0) &&
- do_signal_stop(0))
+ if (unlikely(current->group_stop &
+ GROUP_STOP_PENDING) && do_signal_stop(0))
goto relock;
signr = dequeue_signal(current, ¤t->blocked,
if (!signal_pending(t) && !(t->flags & PF_EXITING))
recalc_sigpending_and_wake(t);
- if (unlikely(tsk->signal->group_stop_count) &&
- !--tsk->signal->group_stop_count) {
- tsk->signal->flags = SIGNAL_STOP_STOPPED;
- group_stop = tracehook_notify_jctl(CLD_STOPPED, CLD_STOPPED);
- }
+ if (unlikely(tsk->group_stop & GROUP_STOP_PENDING) &&
+ task_participate_group_stop(tsk))
+ group_stop = CLD_STOPPED;
out:
spin_unlock_irq(&tsk->sighand->siglock);
+ /*
+ * If group stop has completed, deliver the notification. This
+ * should always go to the real parent of the group leader.
+ */
if (unlikely(group_stop)) {
read_lock(&tasklist_lock);
- do_notify_parent_cldstop(tsk, group_stop);
+ do_notify_parent_cldstop(tsk, false, group_stop);
read_unlock(&tasklist_lock);
}
}
projects / linux-beck.git / blobdiff