From 2140b66b5d3ecf6c7c0fa9dc5eebb41855765ace Mon Sep 17 00:00:00 2001 From: Pierre-Louis Bossart Date: Tue, 14 Jan 2020 18:08:35 -0600 Subject: [PATCH] soundwire: bus: fix race condition with probe_complete signaling The driver probe takes care of basic initialization and is invoked when a Slave becomes attached, after a match between the Slave DevID registers and ACPI/DT entries. The update_status callback is invoked when a Slave state changes, e.g. when it is assigned a non-zero Device Number and it reports with an ATTACHED/ALERT state. The state change detection is usually hardware-based and based on the SoundWire frame rate (e.g. double-digit microseconds) while the probe is a pure software operation, which may involve a kernel module load. In corner cases, it's possible that the state changes before the probe completes. This patch suggests the use of wait_for_completion to avoid races on startup, so that the update_status callback does not rely on invalid pointers/data structures. Signed-off-by: Rander Wang Signed-off-by: Pierre-Louis Bossart Link: https://lore.kernel.org/r/20200115000844.14695-2-pierre-louis.bossart@linux.intel.com Signed-off-by: Vinod Koul --- drivers/soundwire/bus.c | 25 ++++++++++++++++++++++--- drivers/soundwire/bus.h | 1 + drivers/soundwire/bus_type.c | 5 +++++ drivers/soundwire/slave.c | 2 ++ 4 files changed, 30 insertions(+), 3 deletions(-) diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c index 6106577..4980dfd6 100644 --- a/drivers/soundwire/bus.c +++ b/drivers/soundwire/bus.c @@ -970,10 +970,29 @@ 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) { - if (slave->ops && slave->ops->update_status) - return slave->ops->update_status(slave, status); + unsigned long time; - return 0; + if (!slave->probed) { + /* + * the slave status update is typically handled in an + * interrupt thread, which can race with the driver + * probe, e.g. when a module needs to be loaded. + * + * make sure the probe is complete before updating + * status. + */ + time = wait_for_completion_timeout(&slave->probe_complete, + msecs_to_jiffies(DEFAULT_PROBE_TIMEOUT)); + if (!time) { + dev_err(&slave->dev, "Probe not complete, timed out\n"); + return -ETIMEDOUT; + } + } + + if (!slave->ops || !slave->ops->update_status) + return 0; + + return slave->ops->update_status(slave, status); } /** diff --git a/drivers/soundwire/bus.h b/drivers/soundwire/bus.h index cb482da..acb8d11 100644 --- a/drivers/soundwire/bus.h +++ b/drivers/soundwire/bus.h @@ -5,6 +5,7 @@ #define __SDW_BUS_H #define DEFAULT_BANK_SWITCH_TIMEOUT 3000 +#define DEFAULT_PROBE_TIMEOUT 2000 #if IS_ENABLED(CONFIG_ACPI) int sdw_acpi_find_slaves(struct sdw_bus *bus); diff --git a/drivers/soundwire/bus_type.c b/drivers/soundwire/bus_type.c index 4a465f5..17f096d 100644 --- a/drivers/soundwire/bus_type.c +++ b/drivers/soundwire/bus_type.c @@ -110,6 +110,11 @@ static int sdw_drv_probe(struct device *dev) slave->bus->clk_stop_timeout = max_t(u32, slave->bus->clk_stop_timeout, slave->prop.clk_stop_timeout); + slave->probed = true; + complete(&slave->probe_complete); + + dev_dbg(dev, "probe complete\n"); + return 0; } diff --git a/drivers/soundwire/slave.c b/drivers/soundwire/slave.c index 1991997..08db048 100644 --- a/drivers/soundwire/slave.c +++ b/drivers/soundwire/slave.c @@ -47,6 +47,8 @@ static int sdw_slave_add(struct sdw_bus *bus, slave->bus = bus; slave->status = SDW_SLAVE_UNATTACHED; slave->dev_num = 0; + init_completion(&slave->probe_complete); + slave->probed = false; mutex_lock(&bus->bus_lock); list_add_tail(&slave->node, &bus->slaves); -- 2.7.4