* [PATCH] signal: Revert ptrace preempt magic
@ 2018-05-24 14:36 Sebastian Andrzej Siewior
2018-05-24 16:25 ` Eric W. Biederman
0 siblings, 1 reply; 2+ messages in thread
From: Sebastian Andrzej Siewior @ 2018-05-24 14:36 UTC (permalink / raw)
To: linux-kernel
Cc: Miklos Szeredi, Eric W. Biederman, Oleg Nesterov, Thomas Gleixner
From: Thomas Gleixner <tglx@linutronix.de>
Upstream commit '53da1d9456fe7f8 fix ptrace slowness' is nothing more
than a bandaid around the ptrace design trainwreck. It's not a
correctness issue, it's merily a cosmetic bandaid.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
kernel/signal.c | 8 --------
1 file changed, 8 deletions(-)
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1876,15 +1876,7 @@ static void ptrace_stop(int exit_code, i
if (gstop_done && ptrace_reparented(current))
do_notify_parent_cldstop(current, false, why);
- /*
- * Don't want to allow preemption here, because
- * sys_ptrace() needs this task to be inactive.
- *
- * XXX: implement read_unlock_no_resched().
- */
- preempt_disable();
read_unlock(&tasklist_lock);
- preempt_enable_no_resched();
freezable_schedule();
} else {
/*
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH] signal: Revert ptrace preempt magic
2018-05-24 14:36 [PATCH] signal: Revert ptrace preempt magic Sebastian Andrzej Siewior
@ 2018-05-24 16:25 ` Eric W. Biederman
0 siblings, 0 replies; 2+ messages in thread
From: Eric W. Biederman @ 2018-05-24 16:25 UTC (permalink / raw)
To: Sebastian Andrzej Siewior
Cc: linux-kernel, Miklos Szeredi, Oleg Nesterov, Thomas Gleixner
Sebastian Andrzej Siewior <bigeasy@linutronix.de> writes:
> From: Thomas Gleixner <tglx@linutronix.de>
>
> Upstream commit '53da1d9456fe7f8 fix ptrace slowness' is nothing more
> than a bandaid around the ptrace design trainwreck. It's not a
> correctness issue, it's merily a cosmetic bandaid.
This patch comes with no justification or reason to remove the
``cosmetic bandaid''. The description in 53da1d9456fe ("fix ptrace
slowness") is quite persuasive that there is a real world issue.
So while this may be a good idea to remove this. I don't see any
description of testing to indicate this won't cause uml to regresssion.
Nor do I see any compelling reason except code tidiness to remove this.
As such until adequate descriptions can be provideded.
Nacked-by: "Eric W. Biederman" <ebiederm@xmission.com>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> ---
> kernel/signal.c | 8 --------
> 1 file changed, 8 deletions(-)
>
> --- a/kernel/signal.c
> +++ b/kernel/signal.c
> @@ -1876,15 +1876,7 @@ static void ptrace_stop(int exit_code, i
> if (gstop_done && ptrace_reparented(current))
> do_notify_parent_cldstop(current, false, why);
>
> - /*
> - * Don't want to allow preemption here, because
> - * sys_ptrace() needs this task to be inactive.
> - *
> - * XXX: implement read_unlock_no_resched().
> - */
> - preempt_disable();
> read_unlock(&tasklist_lock);
> - preempt_enable_no_resched();
> freezable_schedule();
> } else {
> /*
^ permalink raw reply [flat|nested] 2+ messages in thread
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2018-05-24 14:36 [PATCH] signal: Revert ptrace preempt magic Sebastian Andrzej Siewior
2018-05-24 16:25 ` Eric W. Biederman
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