This is a note to let you know that I've just added the patch titled
powerpc/pseries: Duplicate dtl entries sometimes sent to userspace
to the 3.4-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:
powerpc-pseries-duplicate-dtl-entries-sometimes-sent-to-userspace.patch
and it can be found in the queue-3.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 36d04a55f34ab580aab001e497b97410f0ad5079 Mon Sep 17 00:00:00 2001
From: Anton Blanchard <anton@xxxxxxxxx>
Date: Sun, 17 Nov 2013 11:39:05 +1100
Subject: powerpc/pseries: Duplicate dtl entries sometimes sent to userspace
From: Anton Blanchard <anton@xxxxxxxxx>
commit 84b073868b9d9e754ae48b828337633d1b386482 upstream.
When reading from the dispatch trace log (dtl) userspace interface, I
sometimes see duplicate entries. One example:
# hexdump -C dtl.out
00000000 07 04 00 0c 00 00 48 44 00 00 00 00 00 00 00 00
00000010 00 0c a0 b4 16 83 6d 68 00 00 00 00 00 00 00 00
00000020 00 00 00 00 10 00 13 50 80 00 00 00 00 00 d0 32
00000030 07 04 00 0c 00 00 48 44 00 00 00 00 00 00 00 00
00000040 00 0c a0 b4 16 83 6d 68 00 00 00 00 00 00 00 00
00000050 00 00 00 00 10 00 13 50 80 00 00 00 00 00 d0 32
The problem is in scan_dispatch_log() where we call dtl_consumer()
but bail out before incrementing the index.
To fix this I moved dtl_consumer() after the timebase comparison.
Signed-off-by: Anton Blanchard <anton@xxxxxxxxx>
Signed-off-by: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
Cc: Yijing Wang <wangyijing@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/powerpc/kernel/time.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -212,8 +212,6 @@ static u64 scan_dispatch_log(u64 stop_tb
if (i == vpa->dtl_idx)
return 0;
while (i < vpa->dtl_idx) {
- if (dtl_consumer)
- dtl_consumer(dtl, i);
dtb = dtl->timebase;
tb_delta = dtl->enqueue_to_dispatch_time +
dtl->ready_to_enqueue_time;
@@ -226,6 +224,8 @@ static u64 scan_dispatch_log(u64 stop_tb
}
if (dtb > stop_tb)
break;
+ if (dtl_consumer)
+ dtl_consumer(dtl, i);
stolen += tb_delta;
++i;
++dtl;
Patches currently in stable-queue which might be from anton@xxxxxxxxx are
queue-3.4/powerpc-pseries-duplicate-dtl-entries-sometimes-sent-to-userspace.patch
queue-3.4/powerpc-restore-registers-on-error-exit-from-csum_partial_copy_generic.patch
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