commit b59167ac7bafd804c91e49ad53c6d33a7394d4c8
author Peter Zijlstra <peterz@infradead.org> Thu Oct 11 12:38:27 2018 +0200
committer Thomas Gleixner <tglx@linutronix.de> Sun Oct 14 11:11:22 2018 +0200
tree 9d38b3f253a8c7d60b6717bfd867c456ce586966
parent 4907c68abd3f60f650f98d5a69d4ec77c0bde44f

x86/percpu: Fix this_cpu_read()

Eric reported that a sequence count loop using this_cpu_read() got
optimized out. This is wrong, this_cpu_read() must imply READ_ONCE()
because the interface is IRQ-safe, therefore an interrupt can have
changed the per-cpu value.

Fixes: 7c3576d261ce ("[PATCH] i386: Convert PDA into the percpu section")
Reported-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Eric Dumazet <edumazet@google.com>
Cc: hpa@zytor.com
Cc: eric.dumazet@gmail.com
Cc: bp@alien8.de
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20181011104019.748208519@infradead.org