[PATCH -next] perf bench: fix return value check in do_run_multi_threaded()

[YueHaibing]

In case of error, the function perf_session__new() returns ERR_PTR()
and never returns NULL. The NULL test in the return value check
should be replaced with IS_ERR()

Fixes: 13edc237200c ("perf bench: Add a multi-threaded synthesize benchmark")
Signed-off-by: YueHaibing <yuehaibing@xxxxxxxxxx>
---
 tools/perf/bench/synthesize.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/perf/bench/synthesize.c b/tools/perf/bench/synthesize.c
index 8d624aea1c5e..e39daa609db2 100644
--- a/tools/perf/bench/synthesize.c
+++ b/tools/perf/bench/synthesize.c
@@ -162,8 +162,8 @@ static int do_run_multi_threaded(struct target *target,
 	init_stats(&event_stats);
 	for (i = 0; i < multi_iterations; i++) {
 		session = perf_session__new(NULL, false, NULL);
-		if (!session)
-			return -ENOMEM;
+		if (IS_ERR(session)) {
+			return PTR_ERR(session);
 
 		atomic_set(&event_count, 0);
 		gettimeofday(&start, NULL);
-- 
2.17.1