On Mon, Mar 27, 2017 at 6:09 PM, Alexander Bluhm <alexander.bl...@gmx.net>

> On Mon, Mar 27, 2017 at 05:39:27PM +0200, Mateusz Guzik wrote:
> > The previous patch replaced multiple reads of the global var with just
> > one read and had the result stored in a local variable, which then is
> > read multiple times. Even though the compiler ended up emitting one read
> > of the global, it perfectly legal to emit several, thus the bug can still
> > reappear. This can be prevented as described above.
> It is not a problem when the compiler creates multiple read
> instructions for syslogf as long no function call is between them.
> Nothing else can change the content of syslogf in parallel, we are
> running with the big kernel lock.
> It would be a problem if the compiler would do a read from the
> global syslogf variable before and after a sleep.  But that would
> be illegal in C.

Agreed. I somehow brainfarted myself into not realising it really can't
reload the var across a func call which would be needed to give cpu to
someone else.

Sorry for the noise in that bit.

Mateusz Guzik <mjguzik gmail.com>

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