CVSROOT: /cvs
Module name: src
Changes by: v...@cvs.openbsd.org 2019/02/26 07:24:21
Modified files:
sys/conf : files
sys/kern : init_main.c kern_sched.c sched_bsd.c
sys/sys : sched.h
sys/uvm : uvm_page.c
Added files:
sys/kern : kern_smr.c
sys/sys : smr.h
Log message:
Introduce safe memory reclamation, a mechanism for reclaiming shared
objects that readers can access without locking. This provides a basis
for read-copy-update operations.
Readers access SMR-protected shared objects inside SMR read-side
critical section where sleeping is not allowed. To reclaim
an SMR-protected object, the writer has to ensure mutual exclusion of
other writers, remove the object's shared reference and wait until
read-side references cannot exist any longer. As an alternative to
waiting, the writer can schedule a callback that gets invoked when
reclamation is safe.
The mechanism relies on CPU quiescent states to determine when an
SMR-protected object is ready for reclamation.
The <sys/smr.h> header additionally provides an implementation of
singly- and doubly-linked lists that can be used together with SMR.
These lists allow lockless read access with a concurrent writer.
Discussed with many
OK mpi@ sashan@
