Hi Xiaoming,
On 12/7/20 4:23 PM, Miquel Raynal wrote:
> Hi Xiaoming,
>
> Xiaoming Ni <nixiaoming@xxxxxxxxxx> wrote on Mon, 7 Dec 2020 18:48:33
> +0800:
>
>> ping
>>
>> On 2020/11/27 21:07, Xiaoming Ni wrote:
>>> When CONFIG_MTD_XIP=y, local_irq_disable() is called in xip_disable().
>>> To avoid sleep in interrupt context, we need to call local_irq_enable()
>>> before schedule().
>>>
>>> The problem call stack is as follows:
>>> bug1:
>>> do_write_oneword_retry()
>>> xip_disable()
>>> local_irq_disable()
>>> do_write_oneword_once()
>>> schedule()
>>> bug2:
>>> do_write_buffer()
>>> xip_disable()
>>> local_irq_disable()
>>> do_write_buffer_wait()
>>> schedule()
>>> bug3:
>>> do_erase_chip()
>>> xip_disable()
>>> local_irq_disable()
>>> schedule()
>>> bug4:
>>> do_erase_oneblock()
>>> xip_disable()
>>> local_irq_disable()
>>> schedule()
>>>
>>> Fixes: 02b15e343aee ("[MTD] XIP for AMD CFI flash.")
>>> Cc: stable@xxxxxxxxxxxxxxx # v2.6.13
>>> Signed-off-by: Xiaoming Ni <nixiaoming@xxxxxxxxxx>
>>> ---
>>> drivers/mtd/chips/cfi_cmdset_0002.c | 16 ++++++++++++++++
>>> 1 file changed, 16 insertions(+)
>>>
>>> diff --git a/drivers/mtd/chips/cfi_cmdset_0002.c b/drivers/mtd/chips/cfi_cmdset_0002.c
>>> index a1f3e1031c3d..12c3776f093a 100644
>>> --- a/drivers/mtd/chips/cfi_cmdset_0002.c
>>> +++ b/drivers/mtd/chips/cfi_cmdset_0002.c
>>> @@ -1682,7 +1682,11 @@ static int __xipram do_write_oneword_once(struct map_info *map,
>>> set_current_state(TASK_UNINTERRUPTIBLE);
>>> add_wait_queue(&chip->wq, &wait);
>>> mutex_unlock(&chip->mutex);
>>> + if (IS_ENABLED(CONFIG_MTD_XIP))
>>> + local_irq_enable();
>>> schedule();
>>> + if (IS_ENABLED(CONFIG_MTD_XIP))
>>> + local_irq_disable();
>
> The fix really seems strange to me. I will let Vignesh decide but I
> think we should consider updating/fixing xip_disable instead.
Agree with Miquel. Have you done any testing
or is this purely based on code inspection?
What about comment before xip_disable() function:
/*
* No interrupt what so ever can be serviced while the flash isn't in array
* mode. This is ensured by the xip_disable() and xip_enable() functions
* enclosing any code path where the flash is known not to be in array mode.
* And within a XIP disabled code path, only functions marked with __xipram
* may be called and nothing else (it's a good thing to inspect generated
* assembly to make sure inline functions were actually inlined and that gcc
* didn't emit calls to its own support functions). Also configuring MTD CFI
* support to a single buswidth and a single interleave is also recommended.
*/
So, I don't think the fix is as simple as this patch.
Regards
Vignesh
