On Thu, Jan 04, 2024 at 09:17:08AM +0100, Benjamin Bara wrote:
> From: Benjamin Bara <benjamin.bara@xxxxxxxxxxx>
>
> Since commit aa49c90894d0 ("i2c: core: Run atomic i2c xfer when
> !preemptible"), the whole reboot/power off sequence on non-preempt kernels
> is using atomic i2c xfer, as !preemptible() always results to 1.
>
> During device_shutdown(), the i2c might be used a lot and not all busses
> have implemented an atomic xfer handler. This results in a lot of
> avoidable noise, like:
>
> [ 12.687169] No atomic I2C transfer handler for 'i2c-0'
> [ 12.692313] WARNING: CPU: 6 PID: 275 at drivers/i2c/i2c-core.h:40 i2c_smbus_xfer+0x100/0x118
> ...
>
> Fix this by allowing non-atomic xfer when the interrupts are enabled, as
> it was before.
>
> Fixes: aa49c90894d0 ("i2c: core: Run atomic i2c xfer when !preemptible")
> Cc: stable@xxxxxxxxxxxxxxx # v5.2+
> Signed-off-by: Benjamin Bara <benjamin.bara@xxxxxxxxxxx>
Thanks! The code looks what I also would have suggested reading the bug
reports. So:
Applied to for-current, thanks!
> + /*
> + * non-atomic xfers often use wait_for_completion*() calls to wait
> + * efficiently (schedule out voluntarily) on the completion of the xfer,
> + * which are then "completed" by an IRQ. If the constraints are not
> + * satisfied, fall back to an atomic xfer.
> + */
> + return system_state > SYSTEM_RUNNING &&
> + (IS_ENABLED(CONFIG_PREEMPT_COUNT) ? !preemptible() : irqs_disabled());
I removed the comment, though. I don't think it explains the following
code well enough, i.e. why we have a decision based on a Kconfig
symbol. We can (and should) fix this incrementally, though. I hope this
is OK with everyone.
Thanks to everyone putting work into this. Much appreciated!
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