linux-kernel - Re: [PATCH v4 1/1] coresight/ultrasoc: change smb_drv_data spinlock's type to raw_spinlock

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Message-ID:
 <GV1PR08MB105219ACE97D596BA78FCEE8EFB072@GV1PR08MB10521.eurprd08.prod.outlook.com>
Date: Fri, 20 Dec 2024 10:46:11 +0000
From: Yeo Reum Yun <YeoReum.Yun@....com>
To: Suzuki Poulose <Suzuki.Poulose@....com>, "james.clark@...aro.org"
	<james.clark@...aro.org>, "alexander.shishkin@...ux.intel.com"
	<alexander.shishkin@...ux.intel.com>, "bigeasy@...utronix.de"
	<bigeasy@...utronix.de>, "clrkwllms@...nel.org" <clrkwllms@...nel.org>,
	"rostedt@...dmis.org" <rostedt@...dmis.org>, "mike.leach@...aro.org"
	<mike.leach@...aro.org>
CC: "coresight@...ts.linaro.org" <coresight@...ts.linaro.org>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "linux-rt-devel@...ts.linux.dev"
	<linux-rt-devel@...ts.linux.dev>
Subject: Re: [PATCH v4 1/1] coresight/ultrasoc: change smb_drv_data spinlock's
 type to raw_spinlock_t

Sorry this patch is sent duplicate.

________________________________________
From: Yeoreum Yun <yeoreum.yun@....com>
Sent: 20 December 2024 10:45
To: Suzuki Poulose; james.clark@...aro.org; alexander.shishkin@...ux.intel.com; bigeasy@...utronix.de; clrkwllms@...nel.org; rostedt@...dmis.org; mike.leach@...aro.org
Cc: coresight@...ts.linaro.org; linux-arm-kernel@...ts.infradead.org; linux-kernel@...r.kernel.org; linux-rt-devel@...ts.linux.dev; Yeo Reum Yun
Subject: [PATCH v4 1/1] coresight/ultrasoc: change smb_drv_data spinlock's type to raw_spinlock_t

In ultrasoc-smb drivers, smb_drv_data->spinlock can be held
during __schedule() by perf_event_task_sched_out()/in().

Since smb__drv_data->spinlock type is spinlock_t and
perf_event_task_sched_out()/in() is called after acquiring rq_lock,
which is raw_spinlock_t (an unsleepable lock),
this poses an issue in PREEMPT_RT kernel where spinlock_t is sleepable.

To address this, change type smb_drv_data->spinlock in ultrasoc-smb drivers,
which can be called by perf_event_task_sched_out()/in(),
from spinlock_t to raw_spinlock_t.

Reviewed-by: James Clark <james.clark@...aro.org>
Signed-off-by: Yeoreum Yun <yeoreum.yun@....com>
---
 drivers/hwtracing/coresight/ultrasoc-smb.c | 12 ++++++------
 drivers/hwtracing/coresight/ultrasoc-smb.h |  2 +-
 2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/drivers/hwtracing/coresight/ultrasoc-smb.c b/drivers/hwtracing/coresight/ultrasoc-smb.c
index dc3c9504dd7c..26cfc939e5bd 100644
--- a/drivers/hwtracing/coresight/ultrasoc-smb.c
+++ b/drivers/hwtracing/coresight/ultrasoc-smb.c
@@ -98,7 +98,7 @@ static int smb_open(struct inode *inode, struct file *file)
        struct smb_drv_data *drvdata = container_of(file->private_data,
                                        struct smb_drv_data, miscdev);

-       guard(spinlock)(&drvdata->spinlock);
+       guard(raw_spinlock)(&drvdata->spinlock);

        if (drvdata->reading)
                return -EBUSY;
@@ -152,7 +152,7 @@ static int smb_release(struct inode *inode, struct file *file)
        struct smb_drv_data *drvdata = container_of(file->private_data,
                                        struct smb_drv_data, miscdev);

-       guard(spinlock)(&drvdata->spinlock);
+       guard(raw_spinlock)(&drvdata->spinlock);
        drvdata->reading = false;

        return 0;
@@ -245,7 +245,7 @@ static int smb_enable(struct coresight_device *csdev, enum cs_mode mode,
        struct smb_drv_data *drvdata = dev_get_drvdata(csdev->dev.parent);
        int ret = 0;

-       guard(spinlock)(&drvdata->spinlock);
+       guard(raw_spinlock)(&drvdata->spinlock);

        /* Do nothing, the trace data is reading by other interface now */
        if (drvdata->reading)
@@ -280,7 +280,7 @@ static int smb_disable(struct coresight_device *csdev)
 {
        struct smb_drv_data *drvdata = dev_get_drvdata(csdev->dev.parent);

-       guard(spinlock)(&drvdata->spinlock);
+       guard(raw_spinlock)(&drvdata->spinlock);

        if (drvdata->reading)
                return -EBUSY;
@@ -378,7 +378,7 @@ static unsigned long smb_update_buffer(struct coresight_device *csdev,
        if (!buf)
                return 0;

-       guard(spinlock)(&drvdata->spinlock);
+       guard(raw_spinlock)(&drvdata->spinlock);

        /* Don't do anything if another tracer is using this sink. */
        if (csdev->refcnt != 1)
@@ -563,7 +563,7 @@ static int smb_probe(struct platform_device *pdev)

        smb_reset_buffer(drvdata);
        platform_set_drvdata(pdev, drvdata);
-       spin_lock_init(&drvdata->spinlock);
+       raw_spin_lock_init(&drvdata->spinlock);
        drvdata->pid = -1;

        ret = smb_register_sink(pdev, drvdata);
diff --git a/drivers/hwtracing/coresight/ultrasoc-smb.h b/drivers/hwtracing/coresight/ultrasoc-smb.h
index a91d39cfccb8..c4c111275627 100644
--- a/drivers/hwtracing/coresight/ultrasoc-smb.h
+++ b/drivers/hwtracing/coresight/ultrasoc-smb.h
@@ -115,7 +115,7 @@ struct smb_drv_data {
        struct coresight_device *csdev;
        struct smb_data_buffer sdb;
        struct miscdevice miscdev;
-       spinlock_t spinlock;
+       raw_spinlock_t spinlock;
        bool reading;
        pid_t pid;
 };
--
LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}