[+cc Rafael, linux-pm]
Hi Jia-Ju,
On Mon, Oct 09, 2017 at 04:16:20PM +0800, Jia-Ju Bai wrote:
> The drivers vt6655 and gma500 call pci_set_power_state under a spinlock, which may sleep.
> The function call paths are:
> gma_power_begin (acquire the spinlock) (drivers/gpu/drm/gma500/power.c)
> gma_resume_pci
> pci_set_power_state
> __pci_start_power_transition (drivers/pci/pci.c)
> msleep --> may sleep
>
> gma_power_begin (acquire the spinlock) (drivers/gpu/drm/gma500/power.c)
> gma_resume_pci
> pci_enable_device
> pci_enable_device_flags (drivers/pci/pci.c)
> do_pci_enable_device
> pci_set_power_state
> __pci_start_power_transition
> msleep --> may sleep
>
> vt6655_suspend (acquire the spinlock) (drivers/staging/vt6655/device_main.c)
> pci_set_power_state
> __pci_start_power_transition (drivers/pci/pci.c)
> msleep --> may sleep
>
> To fix these bugs, msleep is replaced with mdelay in __pci_start_power_transition
>
> These bugs are found by my static analysis tool and my code review.
We can either
- change pci_set_power_state() so it can be called while holding a
spinlock (as this patch does), or
- change the drivers so they don't hold the spinlock while calling
pci_set_power_state().
I think the latter is better because d3cold_delay is typically 100ms,
and that's a long time to spin with interrupts disabled.
I assume it's easy to produce an actual failure here? Why haven't we
seen bug reports about this?
Bjorn
> Signed-off-by: Jia-Ju Bai <baijiaju1990@xxxxxxx>
> ---
> drivers/pci/pci.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 6078dfc..7b763a3 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -823,7 +823,7 @@ static void __pci_start_power_transition(struct pci_dev *dev, pci_power_t state)
> */
> if (dev->runtime_d3cold) {
> if (dev->d3cold_delay)
> - msleep(dev->d3cold_delay);
> + mdelay(dev->d3cold_delay);
> /*
> * When powering on a bridge from D3cold, the
> * whole hierarchy may be powered on into
> --
> 1.7.9.5
>
>
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