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From: Ben Hutchings <ben@decadent.org.uk>
To: speck@linutronix.de
Subject: [MODERATED] Re: [PATCH v6 9/9] TAAv6 9
Date: Sun, 13 Oct 2019 21:05:58 +0100	[thread overview]
Message-ID: <67b50974c10173d0399025c96dabc53c1a0e6314.camel@decadent.org.uk> (raw)
In-Reply-To: <20191012014102.GA22297@guptapadev.amr>

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On Fri, 2019-10-11 at 18:41 -0700, speck for Pawan Gupta wrote:
> On Thu, Oct 10, 2019 at 08:54:12AM +0200, speck for Greg KH wrote:
[...]
> > > +/* Take tsx_mutex lock and update tsx_ctrl_state when calling this function */
> > > +static void tsx_update_on_each_cpu(bool val)
> > > +{
> > > +	get_online_cpus();
> > > +	on_each_cpu(tsx_update_this_cpu, (void *)val, 1);
> > > +	put_online_cpus();
> > > +}
> > 
> > Why take the lock?  This is only called in one place.
> 
> So that TSX_CTRL MSR state stays consistent across all CPUs between
> multiple on_each_cpu() calls. Otherwise overlapping conflicting TSX_CTRL MSR
> writes could end up in some CPUs with TSX enabled and others with TSX
> disabled.
[...]

get_online_cpus() is a read lock, so it doesn't prevent concurrent
updates.

Ben.

-- 
Ben Hutchings
The obvious mathematical breakthrough [to break modern encryption]
would be development of an easy way to factor large prime numbers.
                                                           - Bill Gates



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  reply	other threads:[~2019-10-13 20:06 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-09 23:21 [MODERATED] [PATCH v6 0/9] TAAv6 0 Pawan Gupta
2019-10-09 23:22 ` [MODERATED] [PATCH v6 1/9] TAAv6 1 Pawan Gupta
2019-10-09 23:23 ` [MODERATED] [PATCH v6 2/9] TAAv6 2 Pawan Gupta
2019-10-09 23:24 ` [MODERATED] [PATCH v6 3/9] TAAv6 3 Pawan Gupta
2019-10-09 23:25 ` [MODERATED] [PATCH v6 4/9] TAAv6 4 Pawan Gupta
2019-10-09 23:26 ` [MODERATED] [PATCH v6 5/9] TAAv6 5 Pawan Gupta
2019-10-09 23:27 ` [MODERATED] [PATCH v6 6/9] TAAv6 6 Pawan Gupta
2019-10-09 23:28 ` [MODERATED] [PATCH v6 7/9] TAAv6 7 Pawan Gupta
2019-10-09 23:29 ` [MODERATED] [PATCH v6 8/9] TAAv6 8 Pawan Gupta
2019-10-09 23:30 ` [MODERATED] [PATCH v6 9/9] TAAv6 9 Pawan Gupta
2019-10-09 23:34 ` [MODERATED] Re: [PATCH v6 1/9] TAAv6 1 Pawan Gupta
2019-10-10  1:23   ` Pawan Gupta
2019-10-15 12:54     ` Thomas Gleixner
2019-10-21 20:35       ` [MODERATED] " Pawan Gupta
2019-10-09 23:38 ` Andrew Cooper
2019-10-09 23:40   ` Andrew Cooper
2019-10-09 23:53     ` Luck, Tony
2019-10-10  0:01       ` Andrew Cooper
2019-10-10 16:51         ` Luck, Tony
     [not found] ` <5d9e6daa.1c69fb81.f84ad.88ceSMTPIN_ADDED_BROKEN@mx.google.com>
2019-10-10  6:47   ` [MODERATED] Re: [PATCH v6 3/9] TAAv6 3 Greg KH
2019-10-10 23:44     ` Pawan Gupta
     [not found] ` <5d9e6e22.1c69fb81.6df19.ff55SMTPIN_ADDED_BROKEN@mx.google.com>
2019-10-10  6:50   ` [MODERATED] Re: [PATCH v6 5/9] TAAv6 5 Greg KH
2019-10-10 21:18     ` Pawan Gupta
2019-10-10  6:50   ` Greg KH
     [not found] ` <5d9e6f13.1c69fb81.d7036.be99SMTPIN_ADDED_BROKEN@mx.google.com>
2019-10-10  6:54   ` [MODERATED] Re: [PATCH v6 9/9] TAAv6 9 Greg KH
2019-10-12  1:41     ` Pawan Gupta
2019-10-13 20:05       ` Ben Hutchings [this message]
2019-10-13 21:00         ` Ben Hutchings
     [not found] ` <4b15283c29b75be3177eb7c4b8601be5644f630e.157065=?utf-8?q?8889?= .git.pawan.kumar.gupta@linux.intel.com>
2019-10-18  1:21   ` [MODERATED] Re: [PATCH v6 8/9] TAAv6 8 Ben Hutchings
2019-10-21 20:04 ` [MODERATED] Re: [PATCH v6 0/9] TAAv6 0 Josh Poimboeuf
2019-10-21 20:09   ` Pawan Gupta

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