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From: Ingo Molnar <mingo@kernel.org>
To: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: tip-bot for Andy Lutomirski <tipbot@zytor.com>,
	linux-tip-commits@vger.kernel.org, luto@kernel.org,
	hpa@zytor.com, dvlasenk@redhat.com, linux-kernel@vger.kernel.org,
	jann@thejh.net, peterz@infradead.org,
	torvalds@linux-foundation.org, brgerst@gmail.com,
	tglx@linutronix.de, bp@alien8.de
Subject: Re: [tip:x86/asm] x86/dumpstack: Pin the target stack when dumping it
Date: Fri, 16 Sep 2016 14:57:54 +0200
Message-ID: <20160916125754.GA10184@gmail.com> (raw)
In-Reply-To: <20160916122816.lxfa3kmjukjevlrh@treble>


* Josh Poimboeuf <jpoimboe@redhat.com> wrote:

> On Fri, Sep 16, 2016 at 06:55:57AM -0500, Josh Poimboeuf wrote:
> > On Fri, Sep 16, 2016 at 02:17:46AM -0700, tip-bot for Andy Lutomirski wrote:
> > > Commit-ID:  1959a60182f48879635812a03a99c02231ea8677
> > > Gitweb:     http://git.kernel.org/tip/1959a60182f48879635812a03a99c02231ea8677
> > > Author:     Andy Lutomirski <luto@kernel.org>
> > > AuthorDate: Thu, 15 Sep 2016 22:45:45 -0700
> > > Committer:  Ingo Molnar <mingo@kernel.org>
> > > CommitDate: Fri, 16 Sep 2016 09:18:53 +0200
> > > 
> > > x86/dumpstack: Pin the target stack when dumping it
> > > 
> > > Specifically, pin the stack in save_stack_trace_tsk() and
> > > show_trace_log_lvl().
> > > 
> > > This will prevent a crash if the target task dies before or while
> > > dumping its stack once we start freeing task stacks early.
> > 
> > This causes a hang:
> 
> The problem is that show_stack_log_lvl() can be called with a NULL
> task_struct pointer to indicate 'current'.

Could you please send a quick fix that addresses the hang by turning the NULL into 
'current' or so?

> No idea why that convention exists -- IMO we should just require the
> caller to pass 'current' directly.

For hysterical raisins I believe. It appears just a single caller passes 
non-current. Feel free to change this.

Thanks,

	Ingo

  reply index

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-09-16  5:45 [PATCH v2 0/8] thread_info cleanups and stack caching Andy Lutomirski
2016-09-16  5:45 ` [PATCH v2 1/8] x86/entry/64: Fix a minor comment rebase error Andy Lutomirski
2016-09-16  9:16   ` [tip:x86/asm] " tip-bot for Andy Lutomirski
2016-09-16  5:45 ` [PATCH v2 2/8] sched: Add try_get_task_stack() and put_task_stack() Andy Lutomirski
2016-09-16  9:16   ` [tip:x86/asm] sched/core: " tip-bot for Andy Lutomirski
2016-09-16  5:45 ` [PATCH v2 3/8] kthread: to_live_kthread() needs try_get_task_stack() Andy Lutomirski
2016-09-16  9:17   ` [tip:x86/asm] kthread: Pin the stack via try_get_task_stack()/put_task_stack() in to_live_kthread() function tip-bot for Oleg Nesterov
2016-09-16  5:45 ` [PATCH v2 4/8] x86/dumpstack: Pin the target stack when dumping it Andy Lutomirski
2016-09-16  9:17   ` [tip:x86/asm] " tip-bot for Andy Lutomirski
2016-09-16 11:55     ` Josh Poimboeuf
2016-09-16 12:28       ` Josh Poimboeuf
2016-09-16 12:57         ` Ingo Molnar [this message]
2016-09-16 13:05           ` [PATCH] x86/dumpstack: remove NULL task pointer convention Josh Poimboeuf
2016-09-16  5:45 ` [PATCH v2 5/8] x86/process: Pin the target stack in get_wchan() Andy Lutomirski
2016-09-16  9:18   ` [tip:x86/asm] " tip-bot for Andy Lutomirski
2016-09-16  5:45 ` [PATCH v2 6/8] lib/syscall: Pin the task stack in collect_syscall() Andy Lutomirski
2016-09-16  9:18   ` [tip:x86/asm] " tip-bot for Andy Lutomirski
2016-09-16  5:45 ` [PATCH v2 7/8] sched: Free the stack early if CONFIG_THREAD_INFO_IN_TASK Andy Lutomirski
2016-09-16  9:19   ` [tip:x86/asm] sched/core: " tip-bot for Andy Lutomirski
2016-09-16  5:45 ` [PATCH v2 8/8] fork: Cache two thread stacks per cpu if CONFIG_VMAP_STACK is set Andy Lutomirski
2016-09-16  9:19   ` [tip:x86/asm] fork: Optimize task creation by caching two thread stacks per CPU if CONFIG_VMAP_STACK=y tip-bot for Andy Lutomirski

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