linux-kernel - [tip:x86/idle] x86, hotplug: Move WBINVD back outside the play

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <tip-a68e5c94f7d3dd64fef34dd5d97e365cae4bb42a@git.kernel.org>
Date:	Sat, 18 Sep 2010 00:13:05 GMT
From:	"tip-bot for H. Peter Anvin" <hpa@...ux.intel.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
	asit.k.mallick@...el.com, a.p.zijlstra@...llo.hl,
	arjan@...ux.kernel.org, lenb@...nel.org, tglx@...utronix.de,
	hpa@...ux.intel.com, venki@...gle.com
Subject: [tip:x86/idle] x86, hotplug: Move WBINVD back outside the play_dead loop

Commit-ID:  a68e5c94f7d3dd64fef34dd5d97e365cae4bb42a
Gitweb:     http://git.kernel.org/tip/a68e5c94f7d3dd64fef34dd5d97e365cae4bb42a
Author:     H. Peter Anvin <hpa@...ux.intel.com>
AuthorDate: Fri, 17 Sep 2010 17:06:46 -0700
Committer:  H. Peter Anvin <hpa@...ux.intel.com>
CommitDate: Fri, 17 Sep 2010 17:10:23 -0700

x86, hotplug: Move WBINVD back outside the play_dead loop

On processors with hyperthreading, when only one thread is offlined
the other thread can cause a spurious wakeup on the idled thread.  We
do not want to re-WBINVD when that happens.

Ideally, we should simply skip WBINVD unless we're the last thread on
a particular core to shut down, but there might be similar issues
elsewhere in the system.

Thus, revert to previous behavior of only WBINVD outside the loop.
Partly as a result, remove the mb()'s around it: they are not
necessary since wbinvd() is a serializing instruction, but they were
intended to make sure the compiler didn't do any funny loop
optimizations.

Reported-by: Asit Mallick <asit.k.mallick@...el.com>
Signed-off-by: H. Peter Anvin <hpa@...ux.intel.com>
Cc: Arjan van de Ven <arjan@...ux.kernel.org>
Cc: Len Brown <lenb@...nel.org>
Cc: Venkatesh Pallipadi <venki@...gle.com>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.hl>
LKML-Reference: <tip-ea53069231f9317062910d6e772cca4ce93de8c8@....kernel.org>
---
 arch/x86/kernel/smpboot.c |   11 +++++------
 1 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 07bf423..55c80ffb 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1422,9 +1422,9 @@ static inline void mwait_play_dead(void)
 			(highest_subcstate - 1);
 	}
 
+	wbinvd();
+
 	while (1) {
-		mb();
-		wbinvd();
 		__monitor(&current_thread_info()->flags, 0, 0);
 		mb();
 		__mwait(eax, 0);
@@ -1433,11 +1433,10 @@ static inline void mwait_play_dead(void)
 
 static inline void hlt_play_dead(void)
 {
+	if (current_cpu_data.x86 >= 4)
+		wbinvd();
+
 	while (1) {
-		mb();
-		if (current_cpu_data.x86 >= 4)
-			wbinvd();
-		mb();
 		native_halt();
 	}
 }
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/