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coresight: etm4x: Fix etm4_count race by moving cpuhp callbacks to init

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etm4_count keeps track of number of ETMv4 registered and on some systems,
a race is observed on etm4_count variable which can lead to multiple calls
to cpuhp_setup_state_nocalls_cpuslocked(). This function internally calls
cpuhp_store_callbacks() which prevents multiple registrations of callbacks
for a given state and due to this race, it returns -EBUSY leading to ETM
probe failures like below.

 coresight-etm4x: probe of 7040000.etm failed with error -16

This race can easily be triggered with async probe by setting probe type
as PROBE_PREFER_ASYNCHRONOUS and with ETM power management property
"arm,coresight-loses-context-with-cpu".

Prevent this race by moving cpuhp callbacks to etm driver init since the
cpuhp callbacks doesn't have to depend on the etm4_count and can be once
setup during driver init. Similarly we move cpu_pm notifier registration
to driver init and completely remove etm4_count usage. Also now we can
use non cpuslocked version of cpuhp callbacks with this movement.

Fixes: 9b6a3f3633 ("coresight: etmv4: Fix CPU power management setup in probe() function")
Fixes: 58eb457be0 ("hwtracing/coresight-etm4x: Convert to hotplug state machine")
Suggested-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Tested-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Link: https://lore.kernel.org/r/20200916191737.4001561-2-mathieu.poirier@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Sai Prakash Ranjan 2020-09-16 13:17:22 -06:00 committed by Greg Kroah-Hartman
parent 7c33e3c4c7
commit 2d1a8bfb61
1 changed files with 31 additions and 34 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

65
drivers/hwtracing/coresight/coresight-etm4x.c
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@ -48,8 +48,6 @@ module_param(pm_save_enable, int, 0444);
MODULE_PARM_DESC(pm_save_enable,
"Save/restore state on power down: 1 = never, 2 = self-hosted");
/* The number of ETMv4 currently registered */
static int etm4_count;
static struct etmv4_drvdata *etmdrvdata[NR_CPUS];
static void etm4_set_default_config(struct etmv4_config *config);
static int etm4_set_event_filters(struct etmv4_drvdata *drvdata,
@ -1397,28 +1395,25 @@ static struct notifier_block etm4_cpu_pm_nb = {
.notifier_call = etm4_cpu_pm_notify,
};
/* Setup PM. Called with cpus locked. Deals with error conditions and counts */
static int etm4_pm_setup_cpuslocked(void)
/* Setup PM. Deals with error conditions and counts */
static int __init etm4_pm_setup(void)
{
int ret;
if (etm4_count++)
return 0;
ret = cpu_pm_register_notifier(&etm4_cpu_pm_nb);
if (ret)
goto reduce_count;
return ret;
ret = cpuhp_setup_state_nocalls_cpuslocked(CPUHP_AP_ARM_CORESIGHT_STARTING,
"arm/coresight4:starting",
etm4_starting_cpu, etm4_dying_cpu);
ret = cpuhp_setup_state_nocalls(CPUHP_AP_ARM_CORESIGHT_STARTING,
"arm/coresight4:starting",
etm4_starting_cpu, etm4_dying_cpu);
if (ret)
goto unregister_notifier;
ret = cpuhp_setup_state_nocalls_cpuslocked(CPUHP_AP_ONLINE_DYN,
"arm/coresight4:online",
etm4_online_cpu, NULL);
ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
"arm/coresight4:online",
etm4_online_cpu, NULL);
/* HP dyn state ID returned in ret on success */
if (ret > 0) {
@ -1427,21 +1422,15 @@ static int etm4_pm_setup_cpuslocked(void)
}
/* failed dyn state - remove others */
cpuhp_remove_state_nocalls_cpuslocked(CPUHP_AP_ARM_CORESIGHT_STARTING);
cpuhp_remove_state_nocalls(CPUHP_AP_ARM_CORESIGHT_STARTING);
unregister_notifier:
cpu_pm_unregister_notifier(&etm4_cpu_pm_nb);
reduce_count:
--etm4_count;
return ret;
}
static void etm4_pm_clear(void)
static void __init etm4_pm_clear(void)
{
if (--etm4_count != 0)
return;
cpu_pm_unregister_notifier(&etm4_cpu_pm_nb);
cpuhp_remove_state_nocalls(CPUHP_AP_ARM_CORESIGHT_STARTING);
if (hp_online) {
@ -1497,22 +1486,12 @@ static int etm4_probe(struct amba_device *adev, const struct amba_id *id)
if (!desc.name)
return -ENOMEM;
cpus_read_lock();
etmdrvdata[drvdata->cpu] = drvdata;
if (smp_call_function_single(drvdata->cpu,
etm4_init_arch_data, drvdata, 1))
dev_err(dev, "ETM arch init failed\n");
ret = etm4_pm_setup_cpuslocked();
cpus_read_unlock();
/* etm4_pm_setup_cpuslocked() does its own cleanup - exit on error */
if (ret) {
etmdrvdata[drvdata->cpu] = NULL;
return ret;
}
if (etm4_arch_supported(drvdata->arch) == false) {
ret = -EINVAL;
goto err_arch_supported;
@ -1559,7 +1538,6 @@ static int etm4_probe(struct amba_device *adev, const struct amba_id *id)
err_arch_supported:
etmdrvdata[drvdata->cpu] = NULL;
etm4_pm_clear();
return ret;
}
@ -1597,4 +1575,23 @@ static struct amba_driver etm4x_driver = {
.probe = etm4_probe,
.id_table = etm4_ids,
};
builtin_amba_driver(etm4x_driver);
static int __init etm4x_init(void)
{
int ret;
ret = etm4_pm_setup();
/* etm4_pm_setup() does its own cleanup - exit on error */
if (ret)
return ret;
ret = amba_driver_register(&etm4x_driver);
if (ret) {
pr_err("Error registering etm4x driver\n");
etm4_pm_clear();
}
return ret;
}
device_initcall(etm4x_init);