[RFC PATCH] soundwire: use driver callbacks directly with proper locking
In the SoundWire probe, we store a pointer from the driver ops into the 'slave' structure. This can lead to kernel oopses when unbinding codec drivers, e.g. with the following sequence to remove machine driver and codec driver.
/sbin/modprobe -r snd_soc_sof_sdw /sbin/modprobe -r snd_soc_rt711
The full details can be found in the BugLink below, for reference the two following examples show different cases of driver ops/callbacks being invoked after the driver .remove().
kernel: BUG: kernel NULL pointer dereference, address: 0000000000000150 kernel: Workqueue: events cdns_update_slave_status_work [soundwire_cadence] kernel: RIP: 0010:mutex_lock+0x19/0x30 kernel: Call Trace: kernel: ? sdw_handle_slave_status+0x426/0xe00 [soundwire_bus 94ff184bf398570c3f8ff7efe9e32529f532e4ae] kernel: ? newidle_balance+0x26a/0x400 kernel: ? cdns_update_slave_status_work+0x1e9/0x200 [soundwire_cadence 1bcf98eebe5ba9833cd433323769ac923c9c6f82]
kernel: BUG: unable to handle page fault for address: ffffffffc07654c8 kernel: Workqueue: pm pm_runtime_work kernel: RIP: 0010:sdw_bus_prep_clk_stop+0x6f/0x160 [soundwire_bus] kernel: Call Trace: kernel: <TASK> kernel: sdw_cdns_clock_stop+0xb5/0x1b0 [soundwire_cadence 1bcf98eebe5ba9833cd433323769ac923c9c6f82] kernel: intel_suspend_runtime+0x5f/0x120 [soundwire_intel aca858f7c87048d3152a4a41bb68abb9b663a1dd] kernel: ? dpm_sysfs_remove+0x60/0x60
This was not detected earlier in Intel tests since the tests first remove the parent PCI device and shut down the bus. The sequence above is a corner case which keeps the bus operational but without a driver bound.
This patch removes the use the 'slave' ops and uses proper locking to make sure there are no live callbacks based on a dangling pointer executed during or after the driver unbinding sequence. In one specific case, indicated with comments in the code, the device lock is already taken at a higher level when starting the resume operations.
The issue with the ops pointer has been there since December 2017, but there were so many changes in the bus handling code that this patch will not apply cleanly all the way to this initial commit. The changes can be easily backported though.
Thanks to Dan Williams for his suggestions on an earlier version of this patch.
BugLink: https://github.com/thesofproject/linux/issues/3531 Fixes: 56d4fe31af77 ("soundwire: Add MIPI DisCo property helpers") Signed-off-by: Pierre-Louis Bossart pierre-louis.bossart@linux.intel.com ---
This is a follow-up on the initial discussion in https://lore.kernel.org/alsa-devel/d0559e97-c4a0-b817-428c-d3e305390270@linu...
I could use feedback on whether using device_lock() is appropriate and test results on non-Intel platforms. Thanks! Pierre
drivers/soundwire/bus.c | 78 ++++++++++++++++++++++++++++-------- drivers/soundwire/bus_type.c | 6 +-- drivers/soundwire/stream.c | 57 +++++++++++++++++--------- 3 files changed, 102 insertions(+), 39 deletions(-)
diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c index 8b7a680f388e..545b379a119e 100644 --- a/drivers/soundwire/bus.c +++ b/drivers/soundwire/bus.c @@ -7,6 +7,7 @@ #include <linux/pm_runtime.h> #include <linux/soundwire/sdw_registers.h> #include <linux/soundwire/sdw.h> +#include <linux/soundwire/sdw_type.h> #include "bus.h" #include "sysfs_local.h"
@@ -846,12 +847,18 @@ static int sdw_slave_clk_stop_callback(struct sdw_slave *slave, enum sdw_clk_stop_mode mode, enum sdw_clk_stop_type type) { - int ret; + struct device *dev = &slave->dev; + struct sdw_driver *drv;
- if (slave->ops && slave->ops->clk_stop) { - ret = slave->ops->clk_stop(slave, mode, type); - if (ret < 0) - return ret; + /* + * this function can only be called from a pm_runtime + * sequence where the device is already locked + */ + + if (dev->driver) { + drv = drv_to_sdw_driver(dev->driver); + if (drv && drv->ops && drv->ops->clk_stop) + return drv->ops->clk_stop(slave, mode, type); }
return 0; @@ -1616,14 +1623,25 @@ static int sdw_handle_slave_alerts(struct sdw_slave *slave) }
/* Update the Slave driver */ - if (slave_notify && slave->ops && - slave->ops->interrupt_callback) { - slave_intr.sdca_cascade = sdca_cascade; - slave_intr.control_port = clear; - memcpy(slave_intr.port, &port_status, - sizeof(slave_intr.port)); - - slave->ops->interrupt_callback(slave, &slave_intr); + if (slave_notify) { + struct device *dev = &slave->dev; + struct sdw_driver *drv; + + device_lock(dev); + + if (dev->driver) { + drv = drv_to_sdw_driver(dev->driver); + if (drv && drv->ops && drv->ops->interrupt_callback) { + slave_intr.sdca_cascade = sdca_cascade; + slave_intr.control_port = clear; + memcpy(slave_intr.port, &port_status, + sizeof(slave_intr.port)); + + drv->ops->interrupt_callback(slave, &slave_intr); + } + } + + device_unlock(dev); }
/* Ack interrupt */ @@ -1697,7 +1715,12 @@ static int sdw_handle_slave_alerts(struct sdw_slave *slave) static int sdw_update_slave_status(struct sdw_slave *slave, enum sdw_slave_status status) { + struct device *dev = &slave->dev; + struct sdw_driver *drv; unsigned long time; + int ret = 0; + + device_lock_assert(dev);
if (!slave->probed) { /* @@ -1716,10 +1739,13 @@ static int sdw_update_slave_status(struct sdw_slave *slave, } }
- if (!slave->ops || !slave->ops->update_status) - return 0; + if (dev->driver) { + drv = drv_to_sdw_driver(dev->driver); + if (drv && drv->ops && drv->ops->update_status) + ret = drv->ops->update_status(slave, status); + }
- return slave->ops->update_status(slave, status); + return ret; }
/** @@ -1828,7 +1854,10 @@ int sdw_handle_slave_status(struct sdw_bus *bus, break; }
+ device_lock(&slave->dev); ret = sdw_update_slave_status(slave, status[i]); + device_unlock(&slave->dev); + if (ret < 0) dev_err(&slave->dev, "Update Slave status failed:%d\n", ret); @@ -1860,6 +1889,7 @@ EXPORT_SYMBOL(sdw_handle_slave_status); void sdw_clear_slave_status(struct sdw_bus *bus, u32 request) { struct sdw_slave *slave; + bool lock; int i;
/* Check all non-zero devices */ @@ -1878,7 +1908,23 @@ void sdw_clear_slave_status(struct sdw_bus *bus, u32 request) if (slave->status != SDW_SLAVE_UNATTACHED) { sdw_modify_slave_status(slave, SDW_SLAVE_UNATTACHED); slave->first_interrupt_done = false; + + lock = device_trylock(&slave->dev); + + /* + * this bus/manager-level function can only be called from + * a resume sequence. If the peripheral device (child of the + * manager device) is locked, this indicates a resume operation + * initiated by the device core to deal with .remove() or .shutdown() + * at the peripheral level. With the parent-child order enforced + * by PM frameworks on resume, the peripheral resume has not started + * yet, so it's safe to assume the lock will not be released while + * the update_status callback is invoked. + */ sdw_update_slave_status(slave, SDW_SLAVE_UNATTACHED); + + if (lock) + device_unlock(&slave->dev); }
/* keep track of request, used in pm_runtime resume */ diff --git a/drivers/soundwire/bus_type.c b/drivers/soundwire/bus_type.c index 893296f3fe39..91f39c8c119a 100644 --- a/drivers/soundwire/bus_type.c +++ b/drivers/soundwire/bus_type.c @@ -98,8 +98,6 @@ static int sdw_drv_probe(struct device *dev) if (!id) return -ENODEV;
- slave->ops = drv->ops; - /* * attach to power domain but don't turn on (last arg) */ @@ -118,8 +116,8 @@ static int sdw_drv_probe(struct device *dev) }
/* device is probed so let's read the properties now */ - if (slave->ops && slave->ops->read_prop) - slave->ops->read_prop(slave); + if (drv->ops && drv->ops->read_prop) + drv->ops->read_prop(slave);
/* init the sysfs as we have properties now */ ret = sdw_slave_sysfs_init(slave); diff --git a/drivers/soundwire/stream.c b/drivers/soundwire/stream.c index f273459b2023..7862b4403d14 100644 --- a/drivers/soundwire/stream.c +++ b/drivers/soundwire/stream.c @@ -13,6 +13,7 @@ #include <linux/slab.h> #include <linux/soundwire/sdw_registers.h> #include <linux/soundwire/sdw.h> +#include <linux/soundwire/sdw_type.h> #include <sound/soc.h> #include "bus.h"
@@ -401,20 +402,26 @@ static int sdw_do_port_prep(struct sdw_slave_runtime *s_rt, struct sdw_prepare_ch prep_ch, enum sdw_port_prep_ops cmd) { - const struct sdw_slave_ops *ops = s_rt->slave->ops; - int ret; + struct device *dev = &s_rt->slave->dev; + struct sdw_driver *drv; + int ret = 0;
- if (ops->port_prep) { - ret = ops->port_prep(s_rt->slave, &prep_ch, cmd); - if (ret < 0) { - dev_err(&s_rt->slave->dev, - "Slave Port Prep cmd %d failed: %d\n", - cmd, ret); - return ret; + device_lock(dev); + + if (dev->driver) { + drv = drv_to_sdw_driver(dev->driver); + if (drv && drv->ops && drv->ops->port_prep) { + ret = drv->ops->port_prep(s_rt->slave, &prep_ch, cmd); + if (ret < 0) + dev_err(&s_rt->slave->dev, + "Slave Port Prep cmd %d failed: %d\n", + cmd, ret); } }
- return 0; + device_unlock(dev); + + return ret; }
static int sdw_prep_deprep_slave_ports(struct sdw_bus *bus, @@ -578,7 +585,7 @@ static int sdw_notify_config(struct sdw_master_runtime *m_rt) struct sdw_slave_runtime *s_rt; struct sdw_bus *bus = m_rt->bus; struct sdw_slave *slave; - int ret = 0; + int ret;
if (bus->ops->set_bus_conf) { ret = bus->ops->set_bus_conf(bus, &bus->params); @@ -587,19 +594,31 @@ static int sdw_notify_config(struct sdw_master_runtime *m_rt) }
list_for_each_entry(s_rt, &m_rt->slave_rt_list, m_rt_node) { - slave = s_rt->slave; + struct sdw_driver *drv; + struct device *dev;
- if (slave->ops->bus_config) { - ret = slave->ops->bus_config(slave, &bus->params); - if (ret < 0) { - dev_err(bus->dev, "Notify Slave: %d failed\n", - slave->dev_num); - return ret; + slave = s_rt->slave; + dev = &slave->dev; + + device_lock(dev); + + if (dev->driver) { + drv = drv_to_sdw_driver(dev->driver); + if (drv && drv->ops && drv->ops->bus_config) { + ret = drv->ops->bus_config(slave, &bus->params); + if (ret < 0) { + device_unlock(dev); + dev_err(bus->dev, "Notify Slave: %d failed\n", + slave->dev_num); + return ret; + } } } + + device_unlock(dev); }
- return ret; + return 0; }
/**
On 07-04-22, 17:39, Pierre-Louis Bossart wrote:
In the SoundWire probe, we store a pointer from the driver ops into the 'slave' structure. This can lead to kernel oopses when unbinding codec drivers, e.g. with the following sequence to remove machine driver and codec driver.
/sbin/modprobe -r snd_soc_sof_sdw /sbin/modprobe -r snd_soc_rt711
The full details can be found in the BugLink below, for reference the two following examples show different cases of driver ops/callbacks being invoked after the driver .remove().
kernel: BUG: kernel NULL pointer dereference, address: 0000000000000150 kernel: Workqueue: events cdns_update_slave_status_work [soundwire_cadence] kernel: RIP: 0010:mutex_lock+0x19/0x30 kernel: Call Trace: kernel: ? sdw_handle_slave_status+0x426/0xe00 [soundwire_bus 94ff184bf398570c3f8ff7efe9e32529f532e4ae] kernel: ? newidle_balance+0x26a/0x400 kernel: ? cdns_update_slave_status_work+0x1e9/0x200 [soundwire_cadence 1bcf98eebe5ba9833cd433323769ac923c9c6f82]
kernel: BUG: unable to handle page fault for address: ffffffffc07654c8 kernel: Workqueue: pm pm_runtime_work kernel: RIP: 0010:sdw_bus_prep_clk_stop+0x6f/0x160 [soundwire_bus] kernel: Call Trace: kernel: <TASK> kernel: sdw_cdns_clock_stop+0xb5/0x1b0 [soundwire_cadence 1bcf98eebe5ba9833cd433323769ac923c9c6f82] kernel: intel_suspend_runtime+0x5f/0x120 [soundwire_intel aca858f7c87048d3152a4a41bb68abb9b663a1dd] kernel: ? dpm_sysfs_remove+0x60/0x60
This was not detected earlier in Intel tests since the tests first remove the parent PCI device and shut down the bus. The sequence above is a corner case which keeps the bus operational but without a driver bound.
This patch removes the use the 'slave' ops and uses proper locking to make sure there are no live callbacks based on a dangling pointer executed during or after the driver unbinding sequence. In one specific case, indicated with comments in the code, the device lock is already taken at a higher level when starting the resume operations.
The issue with the ops pointer has been there since December 2017, but there were so many changes in the bus handling code that this patch will not apply cleanly all the way to this initial commit. The changes can be easily backported though.
Thanks to Dan Williams for his suggestions on an earlier version of this patch.
BugLink: https://github.com/thesofproject/linux/issues/3531 Fixes: 56d4fe31af77 ("soundwire: Add MIPI DisCo property helpers") Signed-off-by: Pierre-Louis Bossart pierre-louis.bossart@linux.intel.com
This is a follow-up on the initial discussion in https://lore.kernel.org/alsa-devel/d0559e97-c4a0-b817-428c-d3e305390270@linu...
I could use feedback on whether using device_lock() is appropriate and
Looking at other uses of device_lock() it seems apt to me
test results on non-Intel platforms. Thanks! Pierre
drivers/soundwire/bus.c | 78 ++++++++++++++++++++++++++++-------- drivers/soundwire/bus_type.c | 6 +-- drivers/soundwire/stream.c | 57 +++++++++++++++++--------- 3 files changed, 102 insertions(+), 39 deletions(-)
diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c index 8b7a680f388e..545b379a119e 100644 --- a/drivers/soundwire/bus.c +++ b/drivers/soundwire/bus.c @@ -7,6 +7,7 @@ #include <linux/pm_runtime.h> #include <linux/soundwire/sdw_registers.h> #include <linux/soundwire/sdw.h> +#include <linux/soundwire/sdw_type.h> #include "bus.h" #include "sysfs_local.h"
@@ -846,12 +847,18 @@ static int sdw_slave_clk_stop_callback(struct sdw_slave *slave, enum sdw_clk_stop_mode mode, enum sdw_clk_stop_type type) {
- int ret;
- struct device *dev = &slave->dev;
- struct sdw_driver *drv;
- if (slave->ops && slave->ops->clk_stop) {
ret = slave->ops->clk_stop(slave, mode, type);if (ret < 0)return ret;
- /*
* this function can only be called from a pm_runtime* sequence where the device is already locked*/
If this is guaranteed..
- if (dev->driver) {
do we need to check this? Did you find a case where this was not valid while device is locked, maybe do this while holding the lock (kind of moot to process the calls if driver is gone)
drv = drv_to_sdw_driver(dev->driver);if (drv && drv->ops && drv->ops->clk_stop)return drv->ops->clk_stop(slave, mode, type);}
return 0;
@@ -1616,14 +1623,25 @@ static int sdw_handle_slave_alerts(struct sdw_slave *slave) }
/* Update the Slave driver */
if (slave_notify && slave->ops &&slave->ops->interrupt_callback) {slave_intr.sdca_cascade = sdca_cascade;slave_intr.control_port = clear;memcpy(slave_intr.port, &port_status,sizeof(slave_intr.port));slave->ops->interrupt_callback(slave, &slave_intr);
if (slave_notify) {struct device *dev = &slave->dev;struct sdw_driver *drv;device_lock(dev);
device is locked
if (dev->driver) {
Same here as well
drv = drv_to_sdw_driver(dev->driver);if (drv && drv->ops && drv->ops->interrupt_callback) {slave_intr.sdca_cascade = sdca_cascade;slave_intr.control_port = clear;memcpy(slave_intr.port, &port_status,sizeof(slave_intr.port));drv->ops->interrupt_callback(slave, &slave_intr);}}device_unlock(dev);}
/* Ack interrupt */
@@ -1697,7 +1715,12 @@ static int sdw_handle_slave_alerts(struct sdw_slave *slave) static int sdw_update_slave_status(struct sdw_slave *slave, enum sdw_slave_status status) {
struct device *dev = &slave->dev;
struct sdw_driver *drv; unsigned long time;
int ret = 0;
device_lock_assert(dev);
if (!slave->probed) { /*
@@ -1716,10 +1739,13 @@ static int sdw_update_slave_status(struct sdw_slave *slave, } }
- if (!slave->ops || !slave->ops->update_status)
return 0;
- if (dev->driver) {
drv = drv_to_sdw_driver(dev->driver);if (drv && drv->ops && drv->ops->update_status)ret = drv->ops->update_status(slave, status);- }
- return slave->ops->update_status(slave, status);
- return ret;
}
/** @@ -1828,7 +1854,10 @@ int sdw_handle_slave_status(struct sdw_bus *bus, break; }
device_lock(&slave->dev);device_unlock(&slave->dev);- if (ret < 0) dev_err(&slave->dev, "Update Slave status failed:%d\n", ret);
@@ -1860,6 +1889,7 @@ EXPORT_SYMBOL(sdw_handle_slave_status); void sdw_clear_slave_status(struct sdw_bus *bus, u32 request) { struct sdw_slave *slave;
bool lock; int i;
/* Check all non-zero devices */
@@ -1878,7 +1908,23 @@ void sdw_clear_slave_status(struct sdw_bus *bus, u32 request) if (slave->status != SDW_SLAVE_UNATTACHED) { sdw_modify_slave_status(slave, SDW_SLAVE_UNATTACHED); slave->first_interrupt_done = false;
lock = device_trylock(&slave->dev);
should we proceed if we dont get a lock? also why the trylock variant. We can do the lock, this is wq context
/** this bus/manager-level function can only be called from* a resume sequence. If the peripheral device (child of the* manager device) is locked, this indicates a resume operation* initiated by the device core to deal with .remove() or .shutdown()* at the peripheral level. With the parent-child order enforced* by PM frameworks on resume, the peripheral resume has not started* yet, so it's safe to assume the lock will not be released while* the update_status callback is invoked.*/ sdw_update_slave_status(slave, SDW_SLAVE_UNATTACHED);if (lock)device_unlock(&slave->dev);}
/* keep track of request, used in pm_runtime resume */
diff --git a/drivers/soundwire/bus_type.c b/drivers/soundwire/bus_type.c index 893296f3fe39..91f39c8c119a 100644 --- a/drivers/soundwire/bus_type.c +++ b/drivers/soundwire/bus_type.c @@ -98,8 +98,6 @@ static int sdw_drv_probe(struct device *dev) if (!id) return -ENODEV;
- slave->ops = drv->ops;
- /*
*/
- attach to power domain but don't turn on (last arg)
@@ -118,8 +116,8 @@ static int sdw_drv_probe(struct device *dev) }
/* device is probed so let's read the properties now */
- if (slave->ops && slave->ops->read_prop)
slave->ops->read_prop(slave);
if (drv->ops && drv->ops->read_prop)
drv->ops->read_prop(slave);/* init the sysfs as we have properties now */ ret = sdw_slave_sysfs_init(slave);
diff --git a/drivers/soundwire/stream.c b/drivers/soundwire/stream.c index f273459b2023..7862b4403d14 100644 --- a/drivers/soundwire/stream.c +++ b/drivers/soundwire/stream.c @@ -13,6 +13,7 @@ #include <linux/slab.h> #include <linux/soundwire/sdw_registers.h> #include <linux/soundwire/sdw.h> +#include <linux/soundwire/sdw_type.h> #include <sound/soc.h> #include "bus.h"
@@ -401,20 +402,26 @@ static int sdw_do_port_prep(struct sdw_slave_runtime *s_rt, struct sdw_prepare_ch prep_ch, enum sdw_port_prep_ops cmd) {
- const struct sdw_slave_ops *ops = s_rt->slave->ops;
- int ret;
- struct device *dev = &s_rt->slave->dev;
- struct sdw_driver *drv;
- int ret = 0;
- if (ops->port_prep) {
ret = ops->port_prep(s_rt->slave, &prep_ch, cmd);if (ret < 0) {dev_err(&s_rt->slave->dev,"Slave Port Prep cmd %d failed: %d\n",cmd, ret);return ret;
- device_lock(dev);
- if (dev->driver) {
drv = drv_to_sdw_driver(dev->driver);if (drv && drv->ops && drv->ops->port_prep) {ret = drv->ops->port_prep(s_rt->slave, &prep_ch, cmd);if (ret < 0)dev_err(&s_rt->slave->dev,"Slave Port Prep cmd %d failed: %d\n",cmd, ret);
- return 0;
- device_unlock(dev);
- return ret;
}
static int sdw_prep_deprep_slave_ports(struct sdw_bus *bus, @@ -578,7 +585,7 @@ static int sdw_notify_config(struct sdw_master_runtime *m_rt) struct sdw_slave_runtime *s_rt; struct sdw_bus *bus = m_rt->bus; struct sdw_slave *slave;
- int ret = 0;
int ret;
if (bus->ops->set_bus_conf) { ret = bus->ops->set_bus_conf(bus, &bus->params);
@@ -587,19 +594,31 @@ static int sdw_notify_config(struct sdw_master_runtime *m_rt) }
list_for_each_entry(s_rt, &m_rt->slave_rt_list, m_rt_node) {
slave = s_rt->slave;
struct sdw_driver *drv;struct device *dev;
if (slave->ops->bus_config) {ret = slave->ops->bus_config(slave, &bus->params);if (ret < 0) {dev_err(bus->dev, "Notify Slave: %d failed\n",slave->dev_num);return ret;
slave = s_rt->slave;dev = &slave->dev;device_lock(dev);if (dev->driver) {drv = drv_to_sdw_driver(dev->driver);if (drv && drv->ops && drv->ops->bus_config) {ret = drv->ops->bus_config(slave, &bus->params);if (ret < 0) {device_unlock(dev);dev_err(bus->dev, "Notify Slave: %d failed\n",slave->dev_num);return ret;} }device_unlock(dev);
- return ret;
- return 0;
}
/**
2.30.2
Thanks Vinod for the review.
I could use feedback on whether using device_lock() is appropriate and
Looking at other uses of device_lock() it seems apt to me
test results on non-Intel platforms. Thanks! Pierre
drivers/soundwire/bus.c | 78 ++++++++++++++++++++++++++++-------- drivers/soundwire/bus_type.c | 6 +-- drivers/soundwire/stream.c | 57 +++++++++++++++++--------- 3 files changed, 102 insertions(+), 39 deletions(-)
diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c index 8b7a680f388e..545b379a119e 100644 --- a/drivers/soundwire/bus.c +++ b/drivers/soundwire/bus.c @@ -7,6 +7,7 @@ #include <linux/pm_runtime.h> #include <linux/soundwire/sdw_registers.h> #include <linux/soundwire/sdw.h> +#include <linux/soundwire/sdw_type.h> #include "bus.h" #include "sysfs_local.h"
@@ -846,12 +847,18 @@ static int sdw_slave_clk_stop_callback(struct sdw_slave *slave, enum sdw_clk_stop_mode mode, enum sdw_clk_stop_type type) {
- int ret;
- struct device *dev = &slave->dev;
- struct sdw_driver *drv;
- if (slave->ops && slave->ops->clk_stop) {
ret = slave->ops->clk_stop(slave, mode, type);if (ret < 0)return ret;
- /*
* this function can only be called from a pm_runtime* sequence where the device is already locked*/If this is guaranteed..
- if (dev->driver) {
do we need to check this? Did you find a case where this was not valid while device is locked, maybe do this while holding the lock (kind of moot to process the calls if driver is gone)
Humm, good feedback. I will re-check for cases where the driver is 'blacklisted' and also cases there there's no power management supported.
drv = drv_to_sdw_driver(dev->driver);if (drv && drv->ops && drv->ops->clk_stop)return drv->ops->clk_stop(slave, mode, type);
In the last version I did remove the check for if (drv) above since it can't be NULL
}
return 0; @@ -1616,14 +1623,25 @@ static int sdw_handle_slave_alerts(struct sdw_slave *slave) }
/* Update the Slave driver */
if (slave_notify && slave->ops &&slave->ops->interrupt_callback) {slave_intr.sdca_cascade = sdca_cascade;slave_intr.control_port = clear;memcpy(slave_intr.port, &port_status,sizeof(slave_intr.port));slave->ops->interrupt_callback(slave, &slave_intr);
if (slave_notify) {struct device *dev = &slave->dev;struct sdw_driver *drv;device_lock(dev);device is locked
if (dev->driver) {Same here as well
This is a different case. You can have a headset codec that detects a headset and changes it status to alert, even when there is no driver probed. So that case is very real, and it's simpler to think of the sequence backwards.
We have to verify if there is indeed a driver bound before invoking the 'interrupt_callback', otherwise we might de-reference a NULL or dangling pointer. And to prevent a race condition with the .probe/.remove/.shutdown which will modify dev->driver, we have to take the lock before testing dev->driver.
drv = drv_to_sdw_driver(dev->driver);if (drv && drv->ops && drv->ops->interrupt_callback) {slave_intr.sdca_cascade = sdca_cascade;slave_intr.control_port = clear;memcpy(slave_intr.port, &port_status,sizeof(slave_intr.port));drv->ops->interrupt_callback(slave, &slave_intr);}}device_unlock(dev);
/* Check all non-zero devices */ @@ -1878,7 +1908,23 @@ void sdw_clear_slave_status(struct sdw_bus *bus, u32 request) if (slave->status != SDW_SLAVE_UNATTACHED) { sdw_modify_slave_status(slave, SDW_SLAVE_UNATTACHED); slave->first_interrupt_done = false;
lock = device_trylock(&slave->dev);should we proceed if we dont get a lock? also why the trylock variant. We can do the lock, this is wq context
I tried to explain this with the comment below. if we take the lock unconditionally here when it's already taken by the resume sequence, then we created a dead-lock.
This 'sdw_update_slave_status' is invoked from two completely different contexts.
a) the first case is when a manager resumes. In that case, we want to take a lock to prevent .probe or .remove from updating the dev->driver pointer while we're using it. b) the remove is already on-going and the lock was taken by the remove routine. In that case we don't need to take a lock.
So the idea of trylock was to detect which of the two cases we have to deal with.
/** this bus/manager-level function can only be called from* a resume sequence. If the peripheral device (child of the* manager device) is locked, this indicates a resume operation* initiated by the device core to deal with .remove() or .shutdown()* at the peripheral level. With the parent-child order enforced* by PM frameworks on resume, the peripheral resume has not started* yet, so it's safe to assume the lock will not be released while* the update_status callback is invoked.*/ sdw_update_slave_status(slave, SDW_SLAVE_UNATTACHED);if (lock)device_unlock(&slave->dev);
@@ -846,12 +847,18 @@ static int sdw_slave_clk_stop_callback(struct sdw_slave *slave, enum sdw_clk_stop_mode mode, enum sdw_clk_stop_type type) {
- int ret;
- struct device *dev = &slave->dev;
- struct sdw_driver *drv;
- if (slave->ops && slave->ops->clk_stop) {
ret = slave->ops->clk_stop(slave, mode, type);if (ret < 0)return ret;
- /*
* this function can only be called from a pm_runtime* sequence where the device is already locked*/If this is guaranteed..
- if (dev->driver) {
do we need to check this? Did you find a case where this was not valid while device is locked, maybe do this while holding the lock (kind of moot to process the calls if driver is gone)
Humm, good feedback. I will re-check for cases where the driver is 'blacklisted' and also cases there there's no power management supported.
I rechecked all this and it turns out I was mistaken. This function is part of a pm_runtime sequence indeed, but at the parent bus/manager device level. I confused levels and adding a deplock_assert showed very quickly that the peripheral device was never locked.
Thanks for pushing back on this!
In all other cases, I think it's valid and safe to take the lock and test dev->driver. It can happen that there is no driver enabled in the build, or that the driver is 'blacklisted', and in theory the user could muck with sysfs to trigger a peripheral driver binding sequence that would happen smack while the bus is suspended or resume.
I'll do more validation and send an update next week.
-Pierre
participants (2)
-
Pierre-Louis Bossart -
Vinod Koul