On 08/04/2026 2:23 pm, Jie Gan wrote:
Several sysfs show/store handlers check csdev->refcnt before acquiring the spinlock, then access hardware registers inside the lock. This is a race: between the check and the lock acquisition, the following can occur on another CPU:
CPU 0 (sysfs reader) CPU 1 (disable path) ───────────────────────────── ────────────────────────────────── refcnt == 1, check passes [waiting for spinlock] tpda_disable(): refcnt → 0 debug clock disabled spinlock acquired readl_relaxed() ← FAULT/hang
tpda_disable() decrements csdev->refcnt under the same spinlock, so moving the refcnt check inside the lock closes the race.
Fix all six affected sysfs handlers: global_flush_req_show/store, syncr_mode_show, syncr_count_show, and port_flush_req_show/store.
Fixes: 8e1c358a3b0e ("coresight: tpda: add global_flush_req sysfs node") Fixes: 33f04ead7c49 ("coresight: tpda: add logic to configure TPDA_SYNCR register") Fixes: a089d585a7f4 ("coresight: tpda: add sysfs node to flush specific port") Signed-off-by: Jie Gan jie.gan@oss.qualcomm.com
Reviewed-by: James Clark james.clark@linaro.org
drivers/hwtracing/coresight/coresight-tpda.c | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-)
diff --git a/drivers/hwtracing/coresight/coresight-tpda.c b/drivers/hwtracing/coresight/coresight-tpda.c index 89c8f71f0aff..63a979312463 100644 --- a/drivers/hwtracing/coresight/coresight-tpda.c +++ b/drivers/hwtracing/coresight/coresight-tpda.c @@ -360,10 +360,10 @@ static ssize_t global_flush_req_show(struct device *dev, struct tpda_drvdata *drvdata = dev_get_drvdata(dev->parent); unsigned long val;
- guard(spinlock)(&drvdata->spinlock); if (!drvdata->csdev->refcnt) return -EINVAL;
- guard(spinlock)(&drvdata->spinlock); val = readl_relaxed(drvdata->base + TPDA_CR); /* read global_flush_req bit */ val &= TPDA_CR_FLREQ;
@@ -382,10 +382,13 @@ static ssize_t global_flush_req_store(struct device *dev, if (kstrtoul(buf, 0, &val)) return -EINVAL;
- if (!drvdata->csdev->refcnt || !val)
- if (!val) return -EINVAL;
guard(spinlock)(&drvdata->spinlock);
- if (!drvdata->csdev->refcnt)
return -EINVAL;- val = readl_relaxed(drvdata->base + TPDA_CR); /* set global_flush_req bit */ val |= TPDA_CR_FLREQ;
@@ -404,10 +407,10 @@ static ssize_t syncr_mode_show(struct device *dev, struct tpda_drvdata *drvdata = dev_get_drvdata(dev->parent); unsigned long val, syncr_val;
- guard(spinlock)(&drvdata->spinlock); if (!drvdata->csdev->refcnt) return -EINVAL;
- guard(spinlock)(&drvdata->spinlock); syncr_val = readl_relaxed(drvdata->base + TPDA_SYNCR); val = FIELD_GET(TPDA_SYNCR_MODE_CTRL_MASK, syncr_val);
@@ -440,10 +443,10 @@ static ssize_t syncr_count_show(struct device *dev, struct tpda_drvdata *drvdata = dev_get_drvdata(dev->parent); unsigned long val;
- guard(spinlock)(&drvdata->spinlock); if (!drvdata->csdev->refcnt) return -EINVAL;
- guard(spinlock)(&drvdata->spinlock); val = readl_relaxed(drvdata->base + TPDA_SYNCR); val &= TPDA_SYNCR_COUNT_MASK;
@@ -478,10 +481,10 @@ static ssize_t port_flush_req_show(struct device *dev, struct tpda_drvdata *drvdata = dev_get_drvdata(dev->parent); unsigned long val;
- guard(spinlock)(&drvdata->spinlock); if (!drvdata->csdev->refcnt) return -EINVAL;
- guard(spinlock)(&drvdata->spinlock); val = readl_relaxed(drvdata->base + TPDA_FLUSH_CR);
return sysfs_emit(buf, "0x%lx\n", val); @@ -498,10 +501,13 @@ static ssize_t port_flush_req_store(struct device *dev, if (kstrtou32(buf, 0, &val)) return -EINVAL;
- if (!drvdata->csdev->refcnt || !val)
- if (!val) return -EINVAL;
guard(spinlock)(&drvdata->spinlock);
- if (!drvdata->csdev->refcnt)
return -EINVAL;- CS_UNLOCK(drvdata->base); writel_relaxed(val, drvdata->base + TPDA_FLUSH_CR); CS_LOCK(drvdata->base);
base-commit: f3e6330d7fe42b204af05a2dbc68b379e0ad179e change-id: 20260408-fix-race-condition-issue-d44203254b87
Best regards,