PR/59386 CVS commit: [netbsd-10] src/sys/arch/powerpc/powerpc

["Martin Husemann" <martin%netbsd.org@localhost>]

The following reply was made to PR port-powerpc/59386; it has been noted by GNATS.

From: "Martin Husemann" <martin%netbsd.org@localhost>
To: gnats-bugs%gnats.NetBSD.org@localhost
Cc: 
Subject: PR/59386 CVS commit: [netbsd-10] src/sys/arch/powerpc/powerpc
Date: Mon, 5 Jan 2026 14:32:53 +0000

 Module Name:	src
 Committed By:	martin
 Date:		Mon Jan  5 14:32:53 UTC 2026
 
 Modified Files:
 	src/sys/arch/powerpc/powerpc [netbsd-10]: trap_subr.S
 
 Log Message:
 Pull up following revision(s) (requested by jmcneill in ticket #1214):
 
 	sys/arch/powerpc/powerpc/trap_subr.S: revision 1.88
 
 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 -r1.86 -r1.86.4.1 src/sys/arch/powerpc/powerpc/trap_subr.S
 
 Please note that diffs are not public domain; they are subject to the
 copyright notices on the relevant files.