Sorry, I found the latest kernel code has some difference with my analysis. I need more thoughts, then update this issue. > -----Original Message----- > From: Wolfram Sang [mailto:w.sang@xxxxxxxxxxxxxx] > Sent: Monday, July 09, 2012 9:32 PM > To: Liu, Chuansheng > Cc: linux-kernel@xxxxxxxxxxxxxxx; linux-i2c@xxxxxxxxxxxxxxx; khali@xxxxxxxxxxxx; > ben-linux@xxxxxxxxx; Yanmin Zhang <yanmin_zhang@xxxxxxxxxxxxxxx> > (yanmin_zhang@xxxxxxxxxxxxxxx); Srivatsa S. Bhat; Tu, Xiaobing > Subject: Re: [PATCH] i2c_dw: deadlock happening when system is trying to > suspend > > 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/ > | -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
