Roland, could you please explain this code in wait_task_stopped()
if (!exit_code || p->state > TASK_STOPPED)
goto bail_ref;
It looks like "WSTOPPED | WNOWAIT is illegal for TASK_TRACED child"
to me. Is this correct? I think no.
Actually, I don't understand why we are checking p->state at all, we
already dropped tasklist_lock, the state can change at any monent.
Also, wait_task_stopped() calculates ->si_code outside tasklist, is
it correct?
In other words, could you explain why this (untested) patch incorrect ?
Thanks in advance,
Oleg.
--- 2.6.14-rc2/kernel/exit.c~ 2005-09-24 18:33:35.000000000 +0400
+++ 2.6.14-rc2/kernel/exit.c 2005-10-01 00:45:06.000000000 +0400
@@ -1174,10 +1174,13 @@ static int wait_task_stopped(task_t *p,
struct siginfo __user *infop,
int __user *stat_addr, struct rusage __user *ru)
{
- int retval, exit_code;
+ int retval, why, exit_code = p->exit_code;
- if (!p->exit_code)
+ if (!exit_code)
return 0;
+
+ why = (p->ptrace & PT_PTRACED) ? CLD_TRAPPED : CLD_STOPPED;
+
if (delayed_group_leader && !(p->ptrace & PT_PTRACED) &&
p->signal && p->signal->group_stop_count > 0)
/*
@@ -1196,19 +1199,10 @@ static int wait_task_stopped(task_t *p,
get_task_struct(p);
read_unlock(&tasklist_lock);
- if (unlikely(noreap)) {
- pid_t pid = p->pid;
- uid_t uid = p->uid;
- int why = (p->ptrace & PT_PTRACED) ? CLD_TRAPPED : CLD_STOPPED;
-
- exit_code = p->exit_code;
- if (unlikely(!exit_code) ||
- unlikely(p->state > TASK_STOPPED))
- goto bail_ref;
- return wait_noreap_copyout(p, pid, uid,
+ if (unlikely(noreap))
+ return wait_noreap_copyout(p, p->pid, p->uid,
why, (exit_code << 8) | 0x7f,
infop, ru);
- }
write_lock_irq(&tasklist_lock);
@@ -1235,7 +1229,6 @@ static int wait_task_stopped(task_t *p,
* resumed, or it resumed and then died.
*/
write_unlock_irq(&tasklist_lock);
-bail_ref:
put_task_struct(p);
/*
* We are returning to the wait loop without having successfully
@@ -1252,6 +1245,7 @@ bail_ref:
remove_parent(p);
add_parent(p, p->parent);
+ why = (p->ptrace & PT_PTRACED) ? CLD_TRAPPED : CLD_STOPPED;
write_unlock_irq(&tasklist_lock);
retval = ru ? getrusage(p, RUSAGE_BOTH, ru) : 0;
@@ -1262,9 +1256,7 @@ bail_ref:
if (!retval && infop)
retval = put_user(0, &infop->si_errno);
if (!retval && infop)
- retval = put_user((short)((p->ptrace & PT_PTRACED)
- ? CLD_TRAPPED : CLD_STOPPED),
- &infop->si_code);
+ retval = put_user((short)why, &infop->si_code);
if (!retval && infop)
retval = put_user(exit_code, &infop->si_status);
if (!retval && infop)
-
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