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From: Oleg Nesterov <oleg@redhat.com>
To: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Dave Jones <davej@redhat.com>,
	Frederic Weisbecker <fweisbec@gmail.com>,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
	Serge Hallyn <serge.hallyn@canonical.com>,
	linux-kernel@vger.kernel.org
Subject: Re: lots of suspicious RCU traces
Date: Wed, 24 Oct 2012 20:06:08 +0200	[thread overview]
Message-ID: <20121024180608.GA22840@redhat.com> (raw)
In-Reply-To: <20121024164235.GA2467@swordfish>

On 10/24, Sergey Senozhatsky wrote:
>
> small question,
>
> ptrace_notify() and forward calls are able to both indirectly and directly call schedule(),
> /* direct call from ptrace_stop()*/,
> should, in this case, rcu_user_enter() be called before tracehook_report_syscall_exit(regs, step)
> and ptrace chain?

Well, I don't really understand this magic... but why?

Until we return to user-mode this CPU should be in "in_user = false" state.

I am not sure I understand how it is guaranteed that rcu_user_exit() was
called... probably TIF_NOHZ should trigger the slow path and ensure that
syscall_trace_enter()->rcu_user_exit() will be called.

Oleg.


  reply	other threads:[~2012-10-24 18:05 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-10-17  3:49 lots of suspicious RCU traces Dave Jones
2012-10-24 16:42 ` Sergey Senozhatsky
2012-10-24 18:06   ` Oleg Nesterov [this message]
2012-10-24 18:21     ` Sergey Senozhatsky
2012-10-24 18:52       ` Oleg Nesterov
2012-10-24 19:17         ` Sergey Senozhatsky
2012-10-24 19:41           ` Paul E. McKenney
2012-10-24 19:50             ` Sergey Senozhatsky
2012-10-24 20:11               ` Paul E. McKenney
2012-10-24 20:15                 ` Sergey Senozhatsky
2012-10-24 22:32       ` Frederic Weisbecker
2012-10-25  5:50         ` Sergey Senozhatsky
2012-10-25  7:06           ` Frederic Weisbecker
2012-10-25  7:41             ` Sergey Senozhatsky
2012-10-26  9:40               ` [PATCH] rcu: Fix unrecovered RCU user mode in syscall_trace_leave() Frederic Weisbecker
2012-10-26  9:44               ` lots of suspicious RCU traces Frederic Weisbecker
2012-10-26 11:16                 ` Sergey Senozhatsky
2012-10-26 15:16                 ` Dave Jones
2012-10-25  5:55         ` Sergey Senozhatsky

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