CVS commit: src

["Jared D. McNeill" <jmcneill%netbsd.org@localhost>]

Module Name:    src
Committed By:   jmcneill
Date:           Sun Jan  4 11:48:02 UTC 2026

Modified Files:
        src/sys/arch/powerpc/powerpc: trap_subr.S
        src/tests/lib/libc/membar: t_spinlock.c

Log Message:
powerpc: Clear reservations on return from trap.

For MP systems, clear reservations (with stwcx. instruction) when
returning from a trap to protect the following sequence:

  user       kernel
  ----       ------
  lwarx                       # take reservation on address A
             trap             # exception entry
             lwarx            # take reservation on address B
             rfi              # exception return
  stwcx.                      # store with wrong reservation

This can happen both for UP and SMP systems, but I think it's only a
problem for SMP. Since we already clear the reservation on context
switch, there is no risk of another thread storing at the same time.

Fixes PR port-powerpc/59386 (t_spinlock test is failing).


To generate a diff of this commit:
cvs rdiff -u -r1.87 -r1.88 src/sys/arch/powerpc/powerpc/trap_subr.S
cvs rdiff -u -r1.5 -r1.6 src/tests/lib/libc/membar/t_spinlock.c

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