msleep() in interrupt handler?

[Woody Wu]

On Thursday, August 20, 2015, <victorascroft at gmail.com> wrote:

> On 15-08-20 19:02:50, Woody Wu wrote:
> > On Thursday, August 20, 2015, John de la Garza <john at jjdev.com
> <javascript:;>> wrote:
> >
> > > On Thu, Aug 20, 2015 at 01:45:34PM +0800, Woody Wu wrote:
> > > > I did not see the message.  Actually my interrupt handler is calling
> > > > i2c_transfer which in turn used msleep() somewhere in its code.  Is
> this
> > > > normal or dangerous?
> > >
> > > Can you have the interrupt handler put the work on a workqueue
> > > and quickly return?
> > >
> >
> > Yes, that is an option.  But I firstly need to know the old code is
> really
> > bad. The interrupt is triggered by an i2c touchscreen, and  the interrupt
> > handler use the i2c core code to start the i2c transferring.  I see in
> the
> > i2c adapter code a msleep() was invoked at beginning of transfer.  I
> doubt
> > that this is a potential problem.  But you know the i2c touchscreen
> driver
> > code is also part of the mainline, so I am not sure my option.  You guys
> > can check the code of atmel_mXT224_ts.c, the i2c adapter code is
> i2c_s3c.c
>
> I checked the code. The kernel release I am checking in is 4.1.5. From what
> I can see there is only atmel_mxt_ts.c and not atmel_mXT224_ts.c in
> drivers/
> input/touchscreen. In this code, it is requesting a threaded irq with the
> top handler being specified as null and the bottom handler specified.
>
> Since the bottom handler is being used where i2c_transfer is called and
> as such though on a quick check I do not see the msleep() call, even if
> the msleep were called while in the bottom handler context it would be
> fine.
>
> I do not know which code you are referring to but in hard interrupt context
> atleast you can never ever call any function which can sleep. It is just
> gonna blow in some way.
>
> - Sanchayan.
>

The file name you said is right.  The kernel version I am using is 3.1.x,
but I guess it does no much matter to the question. The interrupt handler
of the atmel_mxt_ts called i2c_transfer() which indeed called the actual
i2c adapter's transfer method. In my platform, the i2c adapter is a s3c i2c
controller, so I was checking the code in i2c/busses/i2c_s3c.c, from this
file I saw the msleep() was called in  i2c_doxfer()->i2c_set_master() call
sequence. I think you can find he similar things in 4.1.5.

Thanks.
-woody


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