From: liu chuansheng <chuansheng.liu@xxxxxxxxx>
Subject: [PATCH] i2c_dw: deadlock happening when system is trying to suspend
In i2c_dw code, there is a race condition that causes pm suspend
thread blocking there always. The scenerio is as below:
PM thread:
suspend -->
pm_suspend -->
enter_state -->
dpm_suspend_start(will call i2c_dw_pci_suspend(),
and the dw_i2c_dev->lock is hold)
...
suspend_enter -->
dpm_suspend_noirq -->
suspend_device_irqs -->
synchronize_irq()
synchronize_irq will wait for any pending irq is handled, and
the correpsonding irq thread is finished.
In this case, there is a i2c device interrupt is pending, the irq
thread do the below things:
IRQ thread:
i2c_smbus_read_byte_data -->
i2c_smbus_xfer -->
i2c_transfer -->
i2c_dw_xfer -->
down()
The irq thread blocked at down dw_i2c_dev->lock, because in PM thread,
it has been hold after calling i2c_dw_pci_suspend(), but PM thread is
waiting for IRQ thread, then deadlock happened.
The solution is moving the down() action after pm_runtime_get_sync().
Signed-off-by: liu chuansheng <chuansheng.liu@xxxxxxxxx>
---
drivers/i2c/busses/i2c-designware-core.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/drivers/i2c/busses/i2c-designware-core.c b/drivers/i2c/busses/i2c-designware-core.c
index 1e48bec..748ecb1 100644
--- a/drivers/i2c/busses/i2c-designware-core.c
+++ b/drivers/i2c/busses/i2c-designware-core.c
@@ -512,8 +512,8 @@ i2c_dw_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
dev_dbg(dev->dev, "%s: msgs: %d\n", __func__, num);
- mutex_lock(&dev->lock);
pm_runtime_get_sync(dev->dev);
+ mutex_lock(&dev->lock);
INIT_COMPLETION(dev->cmd_complete);
dev->msgs = msgs;
--
1.7.0.4
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