linux-kernel - Re: Re: [PATCH 1/1] mm: call force_sig

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Message-ID: <20161221092158.GT14217@n2100.armlinux.org.uk>
Date:   Wed, 21 Dec 2016 09:21:59 +0000
From:   Russell King - ARM Linux <linux@...linux.org.uk>
To:     AMIT NAGAL <amit.nagal@...sung.com>
Cc:     Maninder Singh <maninder1.s@...sung.com>,
        "catalin.marinas@....com" <catalin.marinas@....com>,
        "will.deacon@....com" <will.deacon@....com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "jack@...e.cz" <jack@...e.cz>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Ajeet Kumar Yadav <ajeet.y@...sung.com>,
        "shijie.huang@....com" <shijie.huang@....com>,
        "james.morse@....com" <james.morse@....com>,
        "sandeepa.s.prabhu@...il.com" <sandeepa.s.prabhu@...il.com>,
        "labbott@...hat.com" <labbott@...hat.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        PANKAJ MISHRA <pankaj.m@...sung.com>,
        Vaneet Narang <v.narang@...sung.com>
Subject: Re: Re: [PATCH 1/1] mm: call force_sig_info before prints

This is unreadable.  Sorry.

On Wed, Dec 21, 2016 at 05:59:11AM +0000, AMIT NAGAL wrote:
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> <P>Hello,</P><PRE>On Mon, Dec 19, 2016 at 04:07:12PM +0530, Maninder Singh wrote:
> &gt;&gt; prints can delay queuing of signal, so better to print
> &gt;&gt;after force_sig_info.
> &gt;&gt; 
> &gt;&gt; Let's say process generated SIGSEGV , and some other thread sends
> &gt;&gt; SIGKILL to crashing process and it gets queued before SIGSEGV becuase
> &gt;&gt; of little delay due to prints so in this case coredump might not generate.
> 
> &gt; In any case, that's going to be a race - you can't predict exactly when
> &gt; the "other thread" will send the SIGKILL in relation to the SIGSEGV.
> 
> &gt; So, I don't see the point of this change.</PRE><PRE>Actually SIGSEGV queueing gets delayed in __do_user_fault as logs are printed first(show_pte , show_regs).</PRE><PRE>meanwhile if SIGKILL gets queued , SIGSEGV wont be serviced first and coredump will be skipped . </PRE><PRE>so our intention is to queue the SIGSEGV as early as possible . so that the probability of race between</PRE><PRE>SIGKILL and SIGSEGV can be minimized .</PRE><PRE>Amit</PRE><PRE>&nbsp;</PRE><table id=bannersignimg><tr><td><div id="cafe-note-contents" style="margin:10px;font-family:Arial;font-size:10pt;"><p>&nbsp;</p></div></td></tr></table><table id=confidentialsignimg><tr><td><div id="cafe-note-contents" style="margin:10px;font-family:Arial;font-size:10pt;"><p><img unselectable="on" data-cui-image="true" style="display: inline-block; border: 0px solid; width: 520px; height: 144px;" src="cid:cafe_image_0@...ore.co.kr"><br></p></div></td></tr></table></BODY></HTML><img src='http://ext.samsung.net/mail/ext/v1/external/status/update?userid=amit.nagal&do=bWFpbElEPTIwMTYxMjIxMDU1OTExZXBjbXM1cDExNDZjZWU5MjEyY2MxN2ZhOGQ1YjE4YzQ5YTA4NWRlZiZyZWNpcGllbnRBZGRyZXNzPWxpbnV4QGFybWxpbnV4Lm9yZy51aw__' border=0 width=0 height=0 style='display:none'>


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