From: Tom Zanussi <tzanussi@gmail.com>
Date: Mon, 23 Mar 2009 18:41:00 +0000 (+0100)
Subject: Blktrace failed to lock reader threads on the cpu used by the corresponding
X-Git-Tag: blktrace-1.0.1~15
X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=f547a39d32d514eb7bce82b955193b73e9828c85;p=blktrace.git

Blktrace failed to lock reader threads on the cpu used by the corresponding
writer. This resulted in stale data being consumed when blktrace accidently
read at a position that was being written to at the same time. This issue
surfaced as "bad trace magic" warnings emitted by blktrace tools.

The problem occured on an SMP System z machine. The patch fixes the issue.

Signed-off-by: Martin Peschke <mpeschke@linux.vnet.ibm.com>
Signed-off-by: Jens Axboe <axboe@carl.(none)>
---

diff --git a/blktrace.c b/blktrace.c
index 26b3afd..656ab7a 100644
--- a/blktrace.c
+++ b/blktrace.c
@@ -610,7 +610,7 @@ static int lock_on_cpu(int cpu)
 
 	CPU_ZERO(&cpu_mask);
 	CPU_SET(cpu, &cpu_mask);
-	if (sched_setaffinity(getpid(), sizeof(cpu_mask), &cpu_mask) < 0)
+	if (sched_setaffinity(0, sizeof(cpu_mask), &cpu_mask) < 0)
 		return errno;
 
 	return 0;