CVSROOT: /cvs
Module name: src
Changes by: [email protected] 2021/11/05 23:48:47
Modified files:
sys/kern : kern_event.c
Log message:
Make kqread event filter MP-safe
Use the monitored kqueue's kq_lock to serialize kqueue and knote access.
Typically, the "object lock" would cover also the klist, but that is not
possible with kqueues. knote_activate() needs kq_lock of the monitoring
kqueue, which would create lock order troubles if kq_lock was held when
calling KNOTE(&kq->kq_sel.si_note). Avoid this by using a separate klist
lock for kqueues.
The new klist lock is system-wide. Each kqueue instance could have
a dedicated klist lock. However, the efficacy of dedicated versus
system-wide lock is somewhat limited because the current implementation
activates kqueue knotes through a single thread.
OK mpi@
