linux-kernel - Re: RFD: Non-Disruptive Core Dump Infrastructure

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Message-ID: <5230C405.8040108@gmail.com>
Date:	Wed, 11 Sep 2013 15:27:01 -0400
From:	KOSAKI Motohiro <kosaki.motohiro@...il.com>
To:	Janani Venkataraman <jananive@...ux.vnet.ibm.com>
CC:	linux-kernel@...r.kernel.org,
	Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>,
	Daisuke HATAYAMA <d.hatayama@...fujitsu.com>,
	Andi Kleen <andi@...stfloor.org>,
	Roland McGrath <roland@...k.frob.com>,
	Amerigo Wang <amwang@...hat.com>,
	Christoph Hellwig <hch@....de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Masami Hiramatsu <mhiramat@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alexey Dobriyan <adobriyan@...il.com>, xemul@...allels.com,
	Oleg Nesterov <oleg@...hat.com>, Tejun Heo <tj@...nel.org>,
	avagin@...nvz.org, gorcunov@...nvz.org,
	James Hogan <james.hogan@...tec.com>,
	Mike Frysinger <vapier@...too.org>,
	"Randy.Dunlap" <rdunlap@...otime.net>,
	Eric Paris <eparis@...hat.com>, ananth@...ibm.com,
	suzuki@...ibm.com, aravinda@...ux.vnet.ibm.com,
	tarundeep.singh@...ibm.com, kosaki.motohiro@...il.com
Subject: Re: RFD: Non-Disruptive Core Dump Infrastructure

(9/3/13 4:39 AM), Janani Venkataraman wrote:
> Hello,
>
> We are working on an infrastructure to create a system core file of a specific
> process at run-time, non-disruptively. It can also be extended to a case where
> a process is able to take a self-core dump.
>
> gcore, an existing utility creates a core image of the specified process. It
> attaches to the process using gdb and runs the gdb gcore command and then
> detaches. In gcore the dump cannot be issued from a signal handler context as
> fork() is not signal safe and moreover it is disruptive in nature as the gdb
> attaches using ptrace which sends a SIGSTOP signal. Hence the gcore method
> cannot be used if the process wants to initiate a self dump.

Maybe I'm missing something. But why gcore uses c-level fork()? gcore need to
call pthread-at-fork handler? No. gcore need to flush stdio buffer? No.
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