CVS commit: src/sys/dev/dkwedge

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

Module Name:    src
Committed By:   riastradh
Date:           Fri Apr 21 18:25:49 UTC 2023

Modified Files:
        src/sys/dev/dkwedge: dk.c

Log Message:
dk(4): Prevent races in access to struct dkwedge_softc::sc_size.

Rules:

1. Only ever increases, never decreases.

   (Decreases require removing and readding the wedge.)

2. Increases are serialized by dk_openlock.

3. Reads can happen unlocked in any context where the softc is valid.

Access is gathered into dkwedge_size* subroutines -- don't touch
sc_size outside these.  For now, we use rwlock(9) to keep the
reasoning simple.  This should be done with atomics on 64-bit
platforms and a seqlock on 32-bit platforms to avoid contention.
However, we can do that in a later change.


To generate a diff of this commit:
cvs rdiff -u -r1.134 -r1.135 src/sys/dev/dkwedge/dk.c

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