tree f9f5b5ecce4d530e1da06a6a2ce2ef84c7855cc6
parent 2ca97ac8bdcc31fdc868f40c73c017f0a648dc07
author Ahmed S. Darwish <a.darwish@linutronix.de> 1595260529 +0200
committer Peter Zijlstra <peterz@infradead.org> 1596032069 +0200

kvm/eventfd: Use sequence counter with associated spinlock

A sequence counter write side critical section must be protected by some
form of locking to serialize writers. A plain seqcount_t does not
contain the information of which lock must be held when entering a write
side critical section.

Use the new seqcount_spinlock_t data type, which allows to associate a
spinlock with the sequence counter. This enables lockdep to verify that
the spinlock used for writer serialization is held when the write side
critical section is entered.

If lockdep is disabled this lock association is compiled out and has
neither storage size nor runtime overhead.

Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Link: https://lkml.kernel.org/r/20200720155530.1173732-24-a.darwish@linutronix.de