s390/crypto: Replace cond_resched() with msleep(1)

With [1] cond_resched() is always compiled away and becomes a no-op.

The comments for all cond_resched() calls in crypto code however indicate
that the current process should be scheduled away to avoid instant
re-invocation of a callback. This is not what cond_resched() would do or
did.

Instead of just removing the cond_resched() calls, replace them with
msleep() calls, as suggested by Holger Dengler. This forces the current
task to be scheduled away (sleeps) like originally intended.

Holger provided information why this intended [2]:
"
Let me give a bit of background here: The protected key can only get
invalid, if the Linux instance (z/VM or KVM guest) is moved to another
hypervisor on a different machine (aka life guest relocation). In such a
case, the crypto accelerator card and the host has to exchange the "real
key", which is wrapped by the host and handed back to the guest as the
re-newed protected key. Unfortunately there is no asynchronous trigger
on completion, you have to re-try (and maybe get another "in progress"
return).

And as if that weren't bad enough, if this key exchange between card and
host is the first one, card and host has to instantiate a secure
communication channel (including a key exchange for the transport layer).
"

[1] commit 7dadeaa6e851 ("sched: Further restrict the preemption modes")
[2] https://lore.kernel.org/all/39570813-27b0-40f9-89c5-8e2dce05e2f0@linux.ibm.com/
[3] https://lore.kernel.org/all/20260731084027.GE776954@noisy.programming.kicks-ass.net/

[hca@linux.ibm.com: took Peter's patch [3] and provided commit message]

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Reviewed-by: Holger Dengler <dengler@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

0 files changed, 0 insertions, 0 deletions