Re: [PATCH v5 4/4] s390/sclp: Ensure no callback gets called after sclp_unregister() returns

[sashiko-bot@kernel.org]

> There is a potential race condition between sclp_unregister()
> and sclp_dispatch_evbufs()/sclp_dispatch_state_change(). As a result,
> it is not guaranteed that the callbacks registered with sclp_register()
> will not get called one more time (and no more than one) after
> sclp_unregister() returns.
> 
> The basic idea is to use a single global wait queue which is woken up
> when no SCLP WRITE_EVENT_MASK and no SCLP READ_EVENT_DATA request is
> outstanding. If both are true then it is guaranteed that no sclp_register
> callback could be in-flight. Once the struct sclp_register given to
> sclp_unregister() is removed from the list sclp_reg_list, no further
> callbacks can be scheduled for the given struct sclp_register and it only
> remains to wait until the SCLP driver becomes idle.
> 
> With this change sclp_unregister() may no longer be invoked from atomic
> context or registered callbacks. But this represents no problem because
> this is no regular use case and no driver using sclp_unregister() requires
> this at the moment and likely should not require it in the future.
> 
> Signed-off-by: Alexander Egorenkov <egorenar@linux.ibm.com>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20260917065824.2858737-1-egorenar@linux.ibm.com?part=4