Move the code which clears SIGNAL_STOP_STOPPED under "if (force_wakeup)".
Change ptrace_detach() accordingly. See also the next patch which
cleanups/fixes ptrace_wake_up().
Upstream logic:
if detach is explicit, we should always wakeup the tracee,
otherwise (exit_ptrace() path) we rely on ptrace_untrace()
which checks SIGNAL_STOP_STOPPED.
utrace-ptrace:
ptrace_detach(sig) checks valid_signal(sig) to detect the
explicit detach and passes "bool voluntary" to ptrace_wake_up().
both upstream and utrace-ptrace are racy (but these races are
different), hopefully utrace-ptrace is not worse. And of course
this all is not right and should be fixed, but we seem to agree
this should be fixed later, when utrace-ptrace is merged.
In my opinion, from now utrace-ptrace is close enough to upstream
wrt stop/wakeup oddities. It passes all tests which upstream passes,
plus it passes detach-stopped which fails with upstream kernel.
This is because utrace_get_signal() sets SIGNAL_STOP_DEQUEUED when
it returns a sig_kernel_stop() signal. This logic is not exactly
right, but I think it is better than nothing.
IOW: afaics we don't need additional functional changes in this area
before submitting utrace-ptrace. Of course, it is easy to detect the
difference in behaviour and perhaps we will have "it breaks my app"
reports, but I don't think we should try hard to be more bug-compatible
before V1.
What do you think?
---
kernel/ptrace.c | 31 ++++++++++++++++++-------------
1 file changed, 18 insertions(+), 13 deletions(-)
--- PU/kernel/ptrace.c~90_DETACH_CK_IMPLICIT 2009-10-13 19:55:25.000000000
+0200
+++ PU/kernel/ptrace.c 2009-10-14 13:18:45.000000000 +0200
@@ -82,7 +82,8 @@ static int ptrace_attach_task(struct tas
static void ptrace_abort_attach(struct task_struct *tracee);
static void ptrace_wake_up(struct task_struct *tracee,
struct utrace_engine *engine,
- enum utrace_resume_action action);
+ enum utrace_resume_action action,
+ bool force_wakeup);
static struct utrace_engine *ptrace_lookup_engine(struct task_struct *tracee)
{
@@ -92,8 +93,9 @@ static struct utrace_engine *ptrace_look
static void ptrace_detach_task(struct task_struct *tracee, int sig)
{
- struct utrace_engine *engine = ptrace_lookup_engine(tracee);
+ bool voluntary = valid_signal(sig);
enum utrace_resume_action action = UTRACE_DETACH;
+ struct utrace_engine *engine = ptrace_lookup_engine(tracee);
if (unlikely(IS_ERR(engine)))
return;
@@ -104,12 +106,12 @@ static void ptrace_detach_task(struct ta
switch (get_stop_event(context)) {
case PTRACE_EVENT_SYSCALL_ENTRY:
case PTRACE_EVENT_SYSCALL_EXIT:
- if (valid_signal(sig))
+ if (voluntary)
send_sig_info(sig, SEND_SIG_PRIV, tracee);
break;
case PTRACE_EVENT_SIGNAL:
- if (valid_signal(sig))
+ if (voluntary)
context->signr = sig;
context->resume = UTRACE_DETACH;
action = UTRACE_RESUME;
@@ -117,7 +119,7 @@ static void ptrace_detach_task(struct ta
}
}
- ptrace_wake_up(tracee, engine, action);
+ ptrace_wake_up(tracee, engine, action, voluntary);
utrace_engine_put(engine);
}
@@ -944,15 +946,18 @@ void ptrace_notify_stop(struct task_stru
static void ptrace_wake_up( struct task_struct *tracee,
struct utrace_engine *engine,
- enum utrace_resume_action action)
+ enum utrace_resume_action action,
+ bool force_wakeup)
{
- unsigned long flags;
+ if (force_wakeup) {
+ unsigned long flags;
- /* preserve the compatibility bug */
- if (!lock_task_sighand(tracee, &flags))
- return;
- tracee->signal->flags &= ~SIGNAL_STOP_STOPPED;
- unlock_task_sighand(tracee, &flags);
+ /* preserve the compatibility bug */
+ if (!lock_task_sighand(tracee, &flags))
+ return;
+ tracee->signal->flags &= ~SIGNAL_STOP_STOPPED;
+ unlock_task_sighand(tracee, &flags);
+ }
// XXX: FIXME!!! racy.
tracee->exit_code = 0;
@@ -1012,7 +1017,7 @@ static void do_ptrace_resume(struct utra
}
context->resume = action;
- ptrace_wake_up(tracee, engine, action);
+ ptrace_wake_up(tracee, engine, action, true);
}
static int ptrace_resume(struct utrace_engine *engine,
