parisc: Do not use an ordered store in pa_tlb_lock()

No need to use an ordered store in pa_tlb_lock() and update the comment
regarng usage of the sid register to unlocak a spinlock in
tlb_unlock0().

Signed-off-by: John David Anglin <dave.anglin@bell.net>
Signed-off-by: Helge Deller <deller@gmx.de>
Cc: <stable@vger.kernel.org> # v5.0+

diff --git a/arch/parisc/kernel/entry.S b/arch/parisc/kernel/entry.S
index 06455f1..519f905 100644 (file)
--- a/arch/parisc/kernel/entry.S
+++ b/arch/parisc/kernel/entry.S
@@ -455,7 +455,7 @@
        LDREG           0(\ptp),\pte
        bb,<,n          \pte,_PAGE_PRESENT_BIT,3f
        b               \fault
-       stw,ma          \spc,0(\tmp)
+       stw             \spc,0(\tmp)
 99:    ALTERNATIVE(98b, 99b, ALT_COND_NO_SMP, INSN_NOP)
 #endif
 2:     LDREG           0(\ptp),\pte
@@ -463,7 +463,12 @@
 3:
        .endm
 
-       /* Release pa_tlb_lock lock without reloading lock address. */
+       /* Release pa_tlb_lock lock without reloading lock address.
+          Note that the values in the register spc are limited to
+          NR_SPACE_IDS (262144). Thus, the stw instruction always
+          stores a nonzero value even when register spc is 64 bits.
+          We use an ordered store to ensure all prior accesses are
+          performed prior to releasing the lock. */
        .macro          tlb_unlock0     spc,tmp
 #ifdef CONFIG_SMP
 98:    or,COND(=)      %r0,\spc,%r0