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Groups > linux.kernel > #1220131
| From | Tomeu Vizoso <tomeu.vizoso@collabora.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | [PATCH v4 07/22] regulator: core: Reduce critical area in _regulator_get |
| Date | 2015-09-07 14:40 +0200 |
| Message-ID | <q63Sh-5E0-5@gated-at.bofh.it> (permalink) |
| References | <q63IB-5sL-5@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
By moving the locking of regulator_list_mutex into regulator_dev_lookup,
where it is iterated over. The reference count of the regulator's device
is increased in case it's unregistered while in use.
In _regulator_get() the regulator_list_mutex mutex was held for most of
the function, but that is only strictly needed to protect the list
lookups.
This change would be useful if for example regulator devices could be
registered on demand when a driver requests them. regulator_register()
could end up being called from within _regulator_get while the lock on
regulator_list_mutex is being held, causing a deadlock.
This sequence illustrates the situation described above:
tegra_hdmi_probe
_regulator_get
regulator_dev_lookup
of_device_probe
reg_fixed_voltage_probe
regulator_register
Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
---
Changes in v4:
- Take a reference to the regulator's device to prevent dangling
pointers
Changes in v3:
- Avoid unlocking the regulator device's mutex if we don't have a device
Changes in v2:
- Acquire regulator device lock before returning from regulator_dev_lookup()
drivers/regulator/core.c | 56 ++++++++++++++++++++++++++++++++----------------
1 file changed, 38 insertions(+), 18 deletions(-)
diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 7150ff6ef46b..f4aa6cae76d5 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -1340,10 +1340,15 @@ static struct regulator_dev *regulator_dev_lookup(struct device *dev,
if (dev && dev->of_node) {
node = of_get_regulator(dev, supply);
if (node) {
+ mutex_lock(®ulator_list_mutex);
list_for_each_entry(r, ®ulator_list, list)
if (r->dev.parent &&
- node == r->dev.of_node)
+ node == r->dev.of_node &&
+ get_device(&r->dev)) {
+ mutex_unlock(®ulator_list_mutex);
return r;
+ }
+ mutex_unlock(®ulator_list_mutex);
*ret = -EPROBE_DEFER;
return NULL;
} else {
@@ -1361,9 +1366,13 @@ static struct regulator_dev *regulator_dev_lookup(struct device *dev,
if (dev)
devname = dev_name(dev);
+ mutex_lock(®ulator_list_mutex);
list_for_each_entry(r, ®ulator_list, list)
- if (strcmp(rdev_get_name(r), supply) == 0)
+ if (strcmp(rdev_get_name(r), supply) == 0 &&
+ get_device(&r->dev)) {
+ mutex_unlock(®ulator_list_mutex);
return r;
+ }
list_for_each_entry(map, ®ulator_map_list, list) {
/* If the mapping has a device set up it must match */
@@ -1371,9 +1380,13 @@ static struct regulator_dev *regulator_dev_lookup(struct device *dev,
(!devname || strcmp(map->dev_name, devname)))
continue;
- if (strcmp(map->supply, supply) == 0)
+ if (strcmp(map->supply, supply) == 0 &&
+ get_device(&map->regulator->dev)) {
+ mutex_unlock(®ulator_list_mutex);
return map->regulator;
+ }
}
+ mutex_unlock(®ulator_list_mutex);
return NULL;
@@ -1405,6 +1418,7 @@ static int regulator_resolve_supply(struct regulator_dev *rdev)
if (!r) {
if (have_full_constraints()) {
r = dummy_regulator_rdev;
+ get_device(&r->dev);
} else {
dev_err(dev, "Failed to resolve %s-supply for %s\n",
rdev->supply_name, rdev->desc->name);
@@ -1414,12 +1428,16 @@ static int regulator_resolve_supply(struct regulator_dev *rdev)
/* Recursively resolve the supply of the supply */
ret = regulator_resolve_supply(r);
- if (ret < 0)
+ if (ret < 0) {
+ put_device(&r->dev);
return ret;
+ }
ret = set_supply(rdev, r);
- if (ret < 0)
+ if (ret < 0) {
+ put_device(&r->dev);
return ret;
+ }
/* Cascade always-on state to supply */
if (_regulator_is_enabled(rdev) && rdev->supply) {
@@ -1455,8 +1473,6 @@ static struct regulator *_regulator_get(struct device *dev, const char *id,
else
ret = -EPROBE_DEFER;
- mutex_lock(®ulator_list_mutex);
-
rdev = regulator_dev_lookup(dev, id, &ret);
if (rdev)
goto found;
@@ -1468,7 +1484,7 @@ static struct regulator *_regulator_get(struct device *dev, const char *id,
* succeed, so, quit with appropriate error value
*/
if (ret && ret != -ENODEV)
- goto out;
+ return regulator;
if (!devname)
devname = "deviceless";
@@ -1482,40 +1498,46 @@ static struct regulator *_regulator_get(struct device *dev, const char *id,
devname, id);
rdev = dummy_regulator_rdev;
+ get_device(&rdev->dev);
goto found;
/* Don't log an error when called from regulator_get_optional() */
} else if (!have_full_constraints() || exclusive) {
dev_warn(dev, "dummy supplies not allowed\n");
}
- mutex_unlock(®ulator_list_mutex);
return regulator;
found:
if (rdev->exclusive) {
regulator = ERR_PTR(-EPERM);
- goto out;
+ put_device(&rdev->dev);
+ return regulator;
}
if (exclusive && rdev->open_count) {
regulator = ERR_PTR(-EBUSY);
- goto out;
+ put_device(&rdev->dev);
+ return regulator;
}
ret = regulator_resolve_supply(rdev);
if (ret < 0) {
regulator = ERR_PTR(ret);
- goto out;
+ put_device(&rdev->dev);
+ return regulator;
}
- if (!try_module_get(rdev->owner))
- goto out;
+ if (!try_module_get(rdev->owner)) {
+ put_device(&rdev->dev);
+ return regulator;
+ }
regulator = create_regulator(rdev, dev, id);
if (regulator == NULL) {
regulator = ERR_PTR(-ENOMEM);
+ put_device(&rdev->dev);
module_put(rdev->owner);
- goto out;
+ return regulator;
}
rdev->open_count++;
@@ -1529,9 +1551,6 @@ found:
rdev->use_count = 0;
}
-out:
- mutex_unlock(®ulator_list_mutex);
-
return regulator;
}
@@ -1629,6 +1648,7 @@ static void _regulator_put(struct regulator *regulator)
rdev->open_count--;
rdev->exclusive = 0;
+ put_device(&rdev->dev);
mutex_unlock(&rdev->mutex);
kfree(regulator->supply_name);
--
2.4.3
--
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[PATCH v4 0/22] On-demand device probing Tomeu Vizoso <tomeu.vizoso@collabora.com> - 2015-09-07 14:30 +0200
[PATCH v4 13/22] backlight: Probe backlight devices on demand Tomeu Vizoso <tomeu.vizoso@collabora.com> - 2015-09-07 14:30 +0200
[PATCH v4 05/22] gpio: Probe GPIO drivers on demand Tomeu Vizoso <tomeu.vizoso@collabora.com> - 2015-09-07 14:30 +0200
[PATCH v4 03/22] of/platform: Point to struct device from device node Tomeu Vizoso <tomeu.vizoso@collabora.com> - 2015-09-07 14:30 +0200
[PATCH v4 09/22] drm: Probe panels on demand Tomeu Vizoso <tomeu.vizoso@collabora.com> - 2015-09-07 14:30 +0200
[PATCH v4 20/22] driver core: Allow deferring probes until late init Tomeu Vizoso <tomeu.vizoso@collabora.com> - 2015-09-07 14:30 +0200
Re: [PATCH v4 20/22] driver core: Allow deferring probes until late init Mark Brown <broonie@kernel.org> - 2015-09-11 14:20 +0200
Re: [PATCH v4 20/22] driver core: Allow deferring probes until late init Tomeu Vizoso <tomeu.vizoso@collabora.com> - 2015-09-14 11:10 +0200
[PATCH v4 14/22] usb: phy: Probe phy devices on demand Tomeu Vizoso <tomeu.vizoso@collabora.com> - 2015-09-07 14:30 +0200
[PATCH v4 15/22] clk: Probe clk providers on demand Tomeu Vizoso <tomeu.vizoso@collabora.com> - 2015-09-07 14:30 +0200
[PATCH v4 22/22] of/platform: Defer probes of registered devices Tomeu Vizoso <tomeu.vizoso@collabora.com> - 2015-09-07 14:30 +0200
[PATCH v4 16/22] pinctrl: Probe pinctrl devices on demand Tomeu Vizoso <tomeu.vizoso@collabora.com> - 2015-09-07 14:30 +0200
[PATCH v4 21/22] driver core: Start processing deferred probes earlier Tomeu Vizoso <tomeu.vizoso@collabora.com> - 2015-09-07 14:30 +0200
Re: [PATCH v4 21/22] driver core: Start processing deferred probes earlier Mark Brown <broonie@kernel.org> - 2015-09-11 14:30 +0200
Re: [PATCH v4 21/22] driver core: Start processing deferred probes earlier Tomeu Vizoso <tomeu.vizoso@collabora.com> - 2015-09-15 15:20 +0200
[PATCH v4 07/22] regulator: core: Reduce critical area in _regulator_get Tomeu Vizoso <tomeu.vizoso@collabora.com> - 2015-09-07 14:40 +0200
Re: [PATCH v4 07/22] regulator: core: Reduce critical area in _regulator_get Mark Brown <broonie@kernel.org> - 2015-09-11 14:20 +0200
[PATCH v4 11/22] i2c: core: Probe i2c adapters and devices on demand Tomeu Vizoso <tomeu.vizoso@collabora.com> - 2015-09-07 14:40 +0200
[PATCH v4 12/22] pwm: Probe PWM chip devices on demand Tomeu Vizoso <tomeu.vizoso@collabora.com> - 2015-09-07 14:40 +0200
[PATCH v4 02/22] ARM: amba: Move reading of periphid to pre_probe() Tomeu Vizoso <tomeu.vizoso@collabora.com> - 2015-09-07 14:40 +0200
[PATCH v4 01/22] driver core: Add pre_probe callback to bus_type Tomeu Vizoso <tomeu.vizoso@collabora.com> - 2015-09-07 14:40 +0200
Re: [PATCH v4 01/22] driver core: Add pre_probe callback to bus_type Mark Brown <broonie@kernel.org> - 2015-09-11 14:10 +0200
[PATCH v4 10/22] drm/tegra: Probe dpaux devices on demand Tomeu Vizoso <tomeu.vizoso@collabora.com> - 2015-09-07 14:40 +0200
Re: [PATCH v4 0/22] On-demand device probing Rob Herring <robherring2@gmail.com> - 2015-09-07 23:00 +0200
Re: [PATCH v4 0/22] On-demand device probing Tomeu Vizoso <tomeu.vizoso@collabora.com> - 2015-09-08 09:40 +0200
Re: [PATCH v4 0/22] On-demand device probing Rob Herring <robh@kernel.org> - 2015-09-09 07:50 +0200
Re: [PATCH v4 0/22] On-demand device probing Tomeu Vizoso <tomeu.vizoso@collabora.com> - 2015-09-09 11:50 +0200
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