linux-kernel - RE: x86/mce: suspicious RCU usage in 4.13.4

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Message-ID: <3908561D78D1C84285E8C5FCA982C28F770038E5@ORSMSX114.amr.corp.intel.com>
Date:   Wed, 11 Oct 2017 21:34:22 +0000
From:   "Luck, Tony" <tony.luck@...el.com>
To:     Borislav Petkov <bp@...en8.de>, Andi Kleen <ak@...ux.intel.com>
CC:     Jeremy Cline <jcline@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Laura Abbott <labbott@...hat.com>
Subject: RE: x86/mce: suspicious RCU usage in 4.13.4

> here's a second attempt at a more rigorous simplification: RCU stuff is
> gone and only a single loop scans through the elements.

The dev_mce_log() changes look good now.

You can apply the axe to more bits of mce_chrdev_read() though. Like that

	while (!m->finished) {

we hold the mutex, the writer of that holds the mutex ... the spin loop is going to always
time out.  

-Tony