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From:   Suzuki K Poulose <suzuki.poulose@arm.com>
To:     hejunhao3@huawei.com
Cc:     coresight@lists.linaro.org, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, jonathan.cameron@huawei.com,
        leo.yan@linaro.org, mike.leach@linaro.org, james.clark@arm.com,
        linuxarm@huawei.com, yangyicong@huawei.com,
        prime.zeng@hisilicon.com, Suzuki K Poulose <suzuki.poulose@arm.com>
Subject: [PATCH v2 1/2] coresight: trbe: Fix TRBE potential sleep in atomic context
Date:   Wed, 16 Aug 2023 15:10:07 +0100
Message-Id: <20230816141008.535450-1-suzuki.poulose@arm.com>
In-Reply-To: <20230814093813.19152-1-hejunhao3@huawei.com>
References: <20230814093813.19152-1-hejunhao3@huawei.com>
MIME-Version: 1.0
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From: Junhao He <hejunhao3@huawei.com>

smp_call_function_single() will allocate an IPI interrupt vector to
the target processor and send a function call request to the interrupt
vector. After the target processor receives the IPI interrupt, it will
execute arm_trbe_remove_coresight_cpu() call request in the interrupt
handler.

According to the device_unregister() stack information, if other process
is useing the device, the down_write() may sleep, and trigger deadlocks
or unexpected errors.

  arm_trbe_remove_coresight_cpu
    coresight_unregister
      device_unregister
        device_del
          kobject_del
            __kobject_del
              sysfs_remove_dir
                kernfs_remove
                  down_write ---------> it may sleep

Add a helper arm_trbe_disable_cpu() to disable TRBE precpu irq and reset
per TRBE.
Simply call arm_trbe_remove_coresight_cpu() directly without useing the
smp_call_function_single(), which is the same as registering the TRBE
coresight device.

Fixes: 3fbf7f011f24 ("coresight: sink: Add TRBE driver")
Signed-off-by: Junhao He <hejunhao3@huawei.com>
Link: https://lore.kernel.org/r/20230814093813.19152-2-hejunhao3@huawei.com
[ Remove duplicate cpumask checks during removal ]
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
---
 drivers/hwtracing/coresight/coresight-trbe.c | 33 +++++++++++---------
 1 file changed, 18 insertions(+), 15 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-trbe.c b/drivers/hwtracing/coresight/coresight-trbe.c
index 7720619909d6..025f70adee47 100644
--- a/drivers/hwtracing/coresight/coresight-trbe.c
+++ b/drivers/hwtracing/coresight/coresight-trbe.c
@@ -1225,6 +1225,17 @@ static void arm_trbe_enable_cpu(void *info)
 	enable_percpu_irq(drvdata->irq, IRQ_TYPE_NONE);
 }
 
+static void arm_trbe_disable_cpu(void *info)
+{
+	struct trbe_drvdata *drvdata = info;
+	struct trbe_cpudata *cpudata = this_cpu_ptr(drvdata->cpudata);
+
+	disable_percpu_irq(drvdata->irq);
+	trbe_reset_local(cpudata);
+	cpudata->drvdata = NULL;
+}
+
+
 static void arm_trbe_register_coresight_cpu(struct trbe_drvdata *drvdata, int cpu)
 {
 	struct trbe_cpudata *cpudata = per_cpu_ptr(drvdata->cpudata, cpu);
@@ -1326,18 +1337,12 @@ static void arm_trbe_probe_cpu(void *info)
 	cpumask_clear_cpu(cpu, &drvdata->supported_cpus);
 }
 
-static void arm_trbe_remove_coresight_cpu(void *info)
+static void arm_trbe_remove_coresight_cpu(struct trbe_drvdata *drvdata, int cpu)
 {
-	int cpu = smp_processor_id();
-	struct trbe_drvdata *drvdata = info;
-	struct trbe_cpudata *cpudata = per_cpu_ptr(drvdata->cpudata, cpu);
 	struct coresight_device *trbe_csdev = coresight_get_percpu_sink(cpu);
 
-	disable_percpu_irq(drvdata->irq);
-	trbe_reset_local(cpudata);
 	if (trbe_csdev) {
 		coresight_unregister(trbe_csdev);
-		cpudata->drvdata = NULL;
 		coresight_set_percpu_sink(cpu, NULL);
 	}
 }
@@ -1366,8 +1371,10 @@ static int arm_trbe_remove_coresight(struct trbe_drvdata *drvdata)
 {
 	int cpu;
 
-	for_each_cpu(cpu, &drvdata->supported_cpus)
-		smp_call_function_single(cpu, arm_trbe_remove_coresight_cpu, drvdata, 1);
+	for_each_cpu(cpu, &drvdata->supported_cpus) {
+		smp_call_function_single(cpu, arm_trbe_disable_cpu, drvdata, 1);
+		arm_trbe_remove_coresight_cpu(drvdata, cpu);
+	}
 	free_percpu(drvdata->cpudata);
 	return 0;
 }
@@ -1406,12 +1413,8 @@ static int arm_trbe_cpu_teardown(unsigned int cpu, struct hlist_node *node)
 {
 	struct trbe_drvdata *drvdata = hlist_entry_safe(node, struct trbe_drvdata, hotplug_node);
 
-	if (cpumask_test_cpu(cpu, &drvdata->supported_cpus)) {
-		struct trbe_cpudata *cpudata = per_cpu_ptr(drvdata->cpudata, cpu);
-
-		disable_percpu_irq(drvdata->irq);
-		trbe_reset_local(cpudata);
-	}
+	if (cpumask_test_cpu(cpu, &drvdata->supported_cpus))
+		arm_trbe_disable_cpu(drvdata);
 	return 0;
 }
 
-- 
2.34.1