linux-kernel - [stable] [PATCH 1/2] coresight: etb10: Do not call smp_processor

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Message-Id: <20200108110541.318672-1-suzuki.poulose@arm.com>
Date:   Wed,  8 Jan 2020 11:05:40 +0000
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     stable@...r.kernel.org
Cc:     suzuki.poulose@....com, linux-arm-kernel@...ts.infradead.org,
        mathieu.poirier@...aro.org, gregkh@...uxfoundation.org,
        Sasha Levin <sashal@...nel.org>, linux-kernel@...r.kernel.org
Subject: [stable] [PATCH 1/2] coresight: etb10: Do not call smp_processor_id from preemptible

[ Upstream commit 730766bae3280a25d40ea76a53dc6342e84e6513 ]

During a perf session we try to allocate buffers on the "node" associated
with the CPU the event is bound to. If it is not bound to a CPU, we
use the current CPU node, using smp_processor_id(). However this is unsafe
in a pre-emptible context and could generate the splats as below :

 BUG: using smp_processor_id() in preemptible [00000000] code: perf/2544

Use NUMA_NO_NODE hint instead of using the current node for events
not bound to CPUs.

Fixes: 2997aa4063d97fdb39 ("coresight: etb10: implementing AUX API")
Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
Cc: stable <stable@...r.kernel.org> # v4.9 to v4.19
Signed-off-by: Mathieu Poirier <mathieu.poirier@...aro.org>
Link: https://lore.kernel.org/r/20190620221237.3536-5-mathieu.poirier@linaro.org
---
 drivers/hwtracing/coresight/coresight-etb10.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etb10.c b/drivers/hwtracing/coresight/coresight-etb10.c
index 0dad8626bcfb..6cf28b049635 100644
--- a/drivers/hwtracing/coresight/coresight-etb10.c
+++ b/drivers/hwtracing/coresight/coresight-etb10.c
@@ -275,9 +275,7 @@ static void *etb_alloc_buffer(struct coresight_device *csdev, int cpu,
 	int node;
 	struct cs_buffers *buf;
 
-	if (cpu == -1)
-		cpu = smp_processor_id();
-	node = cpu_to_node(cpu);
+	node = (cpu == -1) ? NUMA_NO_NODE : cpu_to_node(cpu);
 
 	buf = kzalloc_node(sizeof(struct cs_buffers), GFP_KERNEL, node);
 	if (!buf)
-- 
2.24.1