3.16.52-rc1 review patch. If anyone has any objections, please let me know.
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From: John David Anglin dave.anglin@bell.net
commit 374b3bf8e8b519f61eb9775888074c6e46b3bf0c upstream.
As discussed on the debian-hppa list, double-wordcompare and exchange operations fail on 32-bit kernels. Looking at the code, I realized that the ",ma" completer does the wrong thing in the "ldw,ma 4(%r26), %r29" instruction. This increments %r26 and causes the following store to write to the wrong location.
Note by Helge Deller: The patch applies cleanly to stable kernel series if this upstream commit is merged in advance: f4125cfdb300 ("parisc: Avoid trashing sr2 and sr3 in LWS code").
Signed-off-by: John David Anglin dave.anglin@bell.net Tested-by: Christoph Biedl debian.axhn@manchmal.in-ulm.de Fixes: 89206491201c ("parisc: Implement new LWS CAS supporting 64 bit operations.") Signed-off-by: Helge Deller deller@gmx.de [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- arch/parisc/kernel/syscall.S | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
--- a/arch/parisc/kernel/syscall.S +++ b/arch/parisc/kernel/syscall.S @@ -742,7 +742,7 @@ lws_compare_and_swap_2: 10: ldd 0(%sr3,%r25), %r25 11: ldd 0(%sr3,%r24), %r24 #else - /* Load new value into r22/r23 - high/low */ + /* Load old value into r22/r23 - high/low */ 10: ldw 0(%sr3,%r25), %r22 11: ldw 4(%sr3,%r25), %r23 /* Load new value into fr4 for atomic store later */ @@ -834,11 +834,11 @@ cas2_action: copy %r0, %r28 #else /* Compare first word */ -19: ldw,ma 0(%sr3,%r26), %r29 +19: ldw 0(%sr3,%r26), %r29 sub,= %r29, %r22, %r0 b,n cas2_end /* Compare second word */ -20: ldw,ma 4(%sr3,%r26), %r29 +20: ldw 4(%sr3,%r26), %r29 sub,= %r29, %r23, %r0 b,n cas2_end /* Perform the store */