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Subject[PATCH 09/16] coresight: cti: Write regsiters directly in cti_enable_hw()
Date
From: Tingwei Zhang <tingwei@codeaurora.org>

Deadlock as below is triggered by one CPU holds drvdata->spinlock
and calls cti_enable_hw(). Smp_call_function_single() is called
in cti_enable_hw() and tries to let another CPU write CTI registers.
That CPU is trying to get drvdata->spinlock in cti_cpu_pm_notify()
and doesn't response to IPI from smp_call_function_single().

[ 988.335937] CPU: 6 PID: 10258 Comm: sh Tainted: G W L
5.8.0-rc6-mainline-16783-gc38daa79b26b-dirty #1
[ 988.346364] Hardware name: Thundercomm Dragonboard 845c (DT)
[ 988.352073] pstate: 20400005 (nzCv daif +PAN -UAO BTYPE=--)
[ 988.357689] pc : smp_call_function_single+0x158/0x1b8
[ 988.362782] lr : smp_call_function_single+0x124/0x1b8
...
[ 988.451638] Call trace:
[ 988.454119] smp_call_function_single+0x158/0x1b8
[ 988.458866] cti_enable+0xb4/0xf8 [coresight_cti]
[ 988.463618] coresight_control_assoc_ectdev+0x6c/0x128 [coresight]
[ 988.469855] coresight_enable+0x1f0/0x364 [coresight]
[ 988.474957] enable_source_store+0x5c/0x9c [coresight]
[ 988.480140] dev_attr_store+0x14/0x28
[ 988.483839] sysfs_kf_write+0x38/0x4c
[ 988.487532] kernfs_fop_write+0x1c0/0x2b0
[ 988.491585] vfs_write+0xfc/0x300
[ 988.494931] ksys_write+0x78/0xe0
[ 988.498283] __arm64_sys_write+0x18/0x20
[ 988.502240] el0_svc_common+0x98/0x160
[ 988.506024] do_el0_svc+0x78/0x80
[ 988.509377] el0_sync_handler+0xd4/0x270
[ 988.513337] el0_sync+0x164/0x180

This change write CTI registers directly in cti_enable_hw().
Config->hw_powered has been checked to be true with spinlock holded.
CTI is powered and can be programmed until spinlock is released.

Fixes: 6a0953ce7de9 ("coresight: cti: Add CPU idle pm notifer to CTI devices")
Signed-off-by: Tingwei Zhang <tingwei@codeaurora.org>
[Re-ordered variable declaration]
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
---
drivers/hwtracing/coresight/coresight-cti.c | 24 +++++----------------
1 file changed, 5 insertions(+), 19 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-cti.c b/drivers/hwtracing/coresight/coresight-cti.c
index c4e9cc7034ab..47f3c9abae30 100644
--- a/drivers/hwtracing/coresight/coresight-cti.c
+++ b/drivers/hwtracing/coresight/coresight-cti.c
@@ -86,22 +86,16 @@ void cti_write_all_hw_regs(struct cti_drvdata *drvdata)
CS_LOCK(drvdata->base);
}

-static void cti_enable_hw_smp_call(void *info)
-{
- struct cti_drvdata *drvdata = info;
-
- cti_write_all_hw_regs(drvdata);
-}
-
/* write regs to hardware and enable */
static int cti_enable_hw(struct cti_drvdata *drvdata)
{
struct cti_config *config = &drvdata->config;
struct device *dev = &drvdata->csdev->dev;
+ unsigned long flags;
int rc = 0;

pm_runtime_get_sync(dev->parent);
- spin_lock(&drvdata->spinlock);
+ spin_lock_irqsave(&drvdata->spinlock, flags);

/* no need to do anything if enabled or unpowered*/
if (config->hw_enabled || !config->hw_powered)
@@ -112,19 +106,11 @@ static int cti_enable_hw(struct cti_drvdata *drvdata)
if (rc)
goto cti_err_not_enabled;

- if (drvdata->ctidev.cpu >= 0) {
- rc = smp_call_function_single(drvdata->ctidev.cpu,
- cti_enable_hw_smp_call,
- drvdata, 1);
- if (rc)
- goto cti_err_not_enabled;
- } else {
- cti_write_all_hw_regs(drvdata);
- }
+ cti_write_all_hw_regs(drvdata);

config->hw_enabled = true;
atomic_inc(&drvdata->config.enable_req_count);
- spin_unlock(&drvdata->spinlock);
+ spin_unlock_irqrestore(&drvdata->spinlock, flags);
return rc;

cti_state_unchanged:
@@ -132,7 +118,7 @@ static int cti_enable_hw(struct cti_drvdata *drvdata)

/* cannot enable due to error */
cti_err_not_enabled:
- spin_unlock(&drvdata->spinlock);
+ spin_unlock_irqrestore(&drvdata->spinlock, flags);
pm_runtime_put(dev->parent);
return rc;
}
--
2.25.1
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