From: tip-bot for Peter Zijlstra <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: hpa@zytor.com, edumazet@google.com, tglx@linutronix.de,
linux-kernel@vger.kernel.org, peterz@infradead.org,
mingo@kernel.org
Subject: [tip:x86/urgent] x86/percpu: Fix this_cpu_read()
Date: Sun, 14 Oct 2018 02:16:33 -0700 [thread overview]
Message-ID: <tip-b59167ac7bafd804c91e49ad53c6d33a7394d4c8@git.kernel.org> (raw)
In-Reply-To: <20181011104019.748208519@infradead.org>
Commit-ID: b59167ac7bafd804c91e49ad53c6d33a7394d4c8
Gitweb: https://git.kernel.org/tip/b59167ac7bafd804c91e49ad53c6d33a7394d4c8
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Thu, 11 Oct 2018 12:38:27 +0200
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitDate: Sun, 14 Oct 2018 11:11:22 +0200
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
---
arch/x86/include/asm/percpu.h | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h
index e9202a0de8f0..1a19d11cfbbd 100644
--- a/arch/x86/include/asm/percpu.h
+++ b/arch/x86/include/asm/percpu.h
@@ -185,22 +185,22 @@ 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; \
prev parent reply other threads:[~2018-10-14 9:18 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-11 10:38 [PATCH 0/2] x86/tsc: Fix native_sched_clock() Peter Zijlstra
2018-10-11 10:38 ` [PATCH 1/2] x86/tsc: Force inlining of cyc2ns bits Peter Zijlstra
2018-10-14 9:15 ` [tip:x86/urgent] " tip-bot for Peter Zijlstra
2018-10-11 10:38 ` [PATCH 2/2] x86/percpu: Fix this_cpu_read() Peter Zijlstra
2018-10-11 15:02 ` Eric Dumazet
2018-10-11 15:24 ` Eric Dumazet
2018-10-11 15:50 ` Peter Zijlstra
2018-10-11 16:08 ` Eric Dumazet
2018-10-14 9:16 ` tip-bot for Peter Zijlstra [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=tip-b59167ac7bafd804c91e49ad53c6d33a7394d4c8@git.kernel.org \
--to=tipbot@zytor.com \
--cc=edumazet@google.com \
--cc=hpa@zytor.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-tip-commits@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=peterz@infradead.org \
--cc=tglx@linutronix.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).