CVS commit: src/sys/kern

["Taylor R Campbell" <riastradh%netbsd.org@localhost>]

Module Name:    src
Committed By:   riastradh
Date:           Thu Feb 23 14:57:29 UTC 2023

Modified Files:
        src/sys/kern: kern_lock.c kern_mutex.c

Log Message:
KERNEL_LOCK(9): Minor tweaks to ci->ci_biglock_wanted access.

1. Use atomic_load_relaxed to read ci->ci_biglock_wanted from another
   CPU, for clarity and to avoid the appearance of data races in thread
   sanitizers.  (Reading ci->ci_biglock_wanted on the local CPU need
   not be atomic because no other CPU can be writing to it.)

2. Use atomic_store_relaxed to update ci->ci_biglock_wanted when we
   start to spin, to avoid the appearance of data races.

3. Add comments to explain what's going on and cross-reference the
   specific matching membars in mutex_vector_enter.

related to PR kern/57240


To generate a diff of this commit:
cvs rdiff -u -r1.182 -r1.183 src/sys/kern/kern_lock.c
cvs rdiff -u -r1.102 -r1.103 src/sys/kern/kern_mutex.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.