On Tue, Jun 26, 2012 at 02:29:13PM +0000, Liu, Chuansheng wrote: > 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; Don't you need to place the mutex_unlock() before pm_runtime_put then? Thanks, Wolfram -- Pengutronix e.K. | Wolfram Sang | Industrial Linux Solutions | http://www.pengutronix.de/ |
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