powerpc/non-smp: Unconditionaly call smp_mb() on switch_mm
Commit 3ccfebedd8 ("powerpc, membarrier: Skip memory barrier in
switch_mm()") added some logic to skip the smp_mb() in
switch_mm_irqs_off() before the call to switch_mmu_context().
However, on non SMP smp_mb() is just a compiler barrier and doing
it unconditionaly is simpler than the logic used to check whether the
barrier is needed or not.
After the patch:
00000000 <switch_mm_irqs_off>:
...
c: 7c 04 18 40 cmplw r4,r3
10: 81 24 00 24 lwz r9,36(r4)
14: 91 25 04 c8 stw r9,1224(r5)
18: 4d 82 00 20 beqlr
1c: 48 00 00 00 b 1c <switch_mm_irqs_off+0x1c>
1c: R_PPC_REL24 switch_mmu_context
Before the patch:
00000000 <switch_mm_irqs_off>:
...
c: 7c 04 18 40 cmplw r4,r3
10: 81 24 00 24 lwz r9,36(r4)
14: 91 25 04 c8 stw r9,1224(r5)
18: 4d 82 00 20 beqlr
1c: 81 24 00 28 lwz r9,40(r4)
20: 71 29 00 0a andi. r9,r9,10
24: 40 82 00 34 bne 58 <switch_mm_irqs_off+0x58>
28: 48 00 00 00 b 28 <switch_mm_irqs_off+0x28>
28: R_PPC_REL24 switch_mmu_context
...
58: 2c 03 00 00 cmpwi r3,0
5c: 41 82 ff cc beq 28 <switch_mm_irqs_off+0x28>
60: 48 00 00 00 b 60 <switch_mm_irqs_off+0x60>
60: R_PPC_REL24 switch_mmu_context
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/e9d501da0c59f60ca767b1b3ea4603fce6d02b9e.1625486440.git.christophe.leroy@csgroup.eu
c8a6d91005