linux-kernel - [PATCH] perf bench numa: Fix assertion for nodes bitfield

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Date:	Sat, 19 Mar 2016 12:58:07 +0100
From:	Jakub Jelen <jakuje@...il.com>
To:	linux-kernel@...r.kernel.org
Cc:	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>, trivial@...nel.org,
	Jakub Jelen <jjelen@...hat.com>, Jakub Jelen <jakuje@...il.com>
Subject: [PATCH] perf bench numa: Fix assertion for nodes bitfield

Comparing bits and bytes in numa benchmark assertion

I hit the issue on two socket Power8 machine presenting its numa nodes as
 0,1,16,17 (according to numactl). Therefore I got error
 (and hang of parent process):

    perf: bench/numa.c:296: bind_to_memnode: Assertion `!(g->p.nr_nodes > (int)sizeof(nodemask))' failed.

This is obviously false positive. We can fit all the 18 nodes into
bitfield of 8 bytes (long on 64b architecture).

Signed-off-by: Jakub Jelen <jakuje@...il.com>
---
Hello kernel list.
This is my first patch for kernel, so if I missed some of the guidelines,
please be patient :) I hope everything is explained in the commit message.

Thanks,
Jakub

 tools/perf/bench/numa.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/bench/numa.c b/tools/perf/bench/numa.c
index 870b7e6..5276b24 100644
--- a/tools/perf/bench/numa.c
+++ b/tools/perf/bench/numa.c
@@ -293,7 +293,7 @@ static void bind_to_memnode(int node)
 	if (node == -1)
 		return;
 
-	BUG_ON(g->p.nr_nodes > (int)sizeof(nodemask));
+	BUG_ON(g->p.nr_nodes > (int)sizeof(nodemask)*8);
 	nodemask = 1L << node;
 
 	ret = set_mempolicy(MPOL_BIND, &nodemask, sizeof(nodemask)*8);
-- 
2.5.0