This is a note to let you know that I've just added the patch titled
x86/percpu: Fix this_cpu_read()
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
x86-percpu-fix-this_cpu_read.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From b59167ac7bafd804c91e49ad53c6d33a7394d4c8 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Date: Thu, 11 Oct 2018 12:38:27 +0200
Subject: x86/percpu: Fix this_cpu_read()
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
commit b59167ac7bafd804c91e49ad53c6d33a7394d4c8 upstream.
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@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Acked-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Cc: hpa@xxxxxxxxx
Cc: eric.dumazet@xxxxxxxxx
Cc: bp@xxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Link: https://lkml.kernel.org/r/20181011104019.748208519@xxxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/include/asm/percpu.h | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
--- a/arch/x86/include/asm/percpu.h
+++ b/arch/x86/include/asm/percpu.h
@@ -184,22 +184,22 @@ do { \
typeof(var) pfo_ret__; \
switch (sizeof(var)) { \
case 1: \
- asm(op "b "__percpu_arg(1)",%0" \
+ asm volatile(op "b "__percpu_arg(1)",%0"\
: "=q" (pfo_ret__) \
: "m" (var)); \
break; \
case 2: \
- asm(op "w "__percpu_arg(1)",%0" \
+ asm volatile(op "w "__percpu_arg(1)",%0"\
: "=r" (pfo_ret__) \
: "m" (var)); \
break; \
case 4: \
- asm(op "l "__percpu_arg(1)",%0" \
+ asm volatile(op "l "__percpu_arg(1)",%0"\
: "=r" (pfo_ret__) \
: "m" (var)); \
break; \
case 8: \
- asm(op "q "__percpu_arg(1)",%0" \
+ asm volatile(op "q "__percpu_arg(1)",%0"\
: "=r" (pfo_ret__) \
: "m" (var)); \
break; \
Patches currently in stable-queue which might be from peterz@xxxxxxxxxxxxx are
queue-4.4/perf-tools-disable-parallelism-for-make-clean.patch
queue-4.4/perf-ring_buffer-prevent-concurent-ring-buffer-acces.patch
queue-4.4/sched-fair-fix-throttle_list-starvation-with-low-cfs-quota.patch
queue-4.4/sched-cgroup-fix-cgroup-entity-load-tracking-tear-do.patch
queue-4.4/perf-core-don-t-leak-event-in-the-syscall-error-path.patch
queue-4.4/tracing-skip-more-functions-when-doing-stack-tracing.patch
queue-4.4/x86-percpu-fix-this_cpu_read.patch
queue-4.4/mremap-properly-flush-tlb-before-releasing-the-page.patch
