Seeing the above message, I added a trivial change to print out the
Mask and Pending, and I consistently saw it was (both p/m) in every
case `was __IRQF_TIMER (0x200).
Looking at do_current_softirqs, it seems that it implicitly expects
two entrance paths:
/*
* Called with interrupts disabled. Process softirqs which were raised
* in current context (or on behalf of ksoftirqd).
*/
static void do_current_softirqs(int need_rcu_bh_qs)
In there, we loop on current->softirqs_raised, but there is no "filter"
for the case where we spawn from ksoftirqd with __IRQF_TIMER, or more
specifically IRQF_NO_THREAD. Asking ksoftirqd to handle IRQF_NO_THREAD?
So based on my dain-bramaged and limited understanding, it seems that
we are waiting on completion from ksoftirqd on something that we've
asked to be not run from a thread. I'd propose a patch but I'd probably
only manage to hurt myself, so I'll stop at reporting the above data,
and leave it to the folks more in the know to suggest a proper fix...
Paul.
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