Re: [PATCH] kunit: irq: Continue increasing hrtimer interval for longer

[Eric Biggers]

On Mon, Aug 03, 2026 at 11:18:41AM -0700, Eric Biggers wrote:
> Currently, kunit_irq_test_timer_func() stops increasing the hrtimer
> interval as soon as some forward progress is made in each of softirq and
> task context.  Update it to use a more aggressive strategy: increase the
> interval as long as the hrtimer is running significantly faster than
> either context.
> 
> This resolves an occasional hang in the CRC and crypto library tests
> under qemu-system-s390x.  It was exposed by the change in the default
> preemption model on s390 from NONE to LAZY.  That seems to have exposed
> the issue by allowing some forward progress to be made while the actual
> system timer tick is still starved, preventing jiffies from increasing
> or the task context from making much progress towards max_iterations.
> 
> Fixes: 201ceb94aa1d ("kunit: irq: Ensure timer doesn't fire too frequently")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
> ---
> 
> This patch is targeting libcrypto-next

Applied to https://git.kernel.org/pub/scm/linux/kernel/git/ebiggers/linux.git/log/?h=libcrypto-next

- Eric