linux-kernel - [PATCH 5.4 246/270] Revert "parisc: Drop LDCW barrier in CAS code when running UP"

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Message-Id: <20200817143808.079367859@linuxfoundation.org>
Date:   Mon, 17 Aug 2020 17:17:27 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Helge Deller <deller@....de>
Subject: [PATCH 5.4 246/270] Revert "parisc: Drop LDCW barrier in CAS code when running UP"

From: Helge Deller <deller@....de>

commit 462fb756c7de1ffe5bc6099149136031c2d9c02a upstream.

This reverts commit e6eb5fe9123f05dcbf339ae5c0b6d32fcc0685d5.
We need to optimize it differently. A follow up patch will correct it.

Signed-off-by: Helge Deller <deller@....de>
Cc: <stable@...r.kernel.org> # v5.2+
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/parisc/kernel/syscall.S |   12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

--- a/arch/parisc/kernel/syscall.S
+++ b/arch/parisc/kernel/syscall.S
@@ -641,8 +641,7 @@ cas_action:
 2:	stw	%r24, 0(%r26)
 	/* Free lock */
 #ifdef CONFIG_SMP
-98:	LDCW	0(%sr2,%r20), %r1			/* Barrier */
-99:	ALTERNATIVE(98b, 99b, ALT_COND_NO_SMP, INSN_NOP)
+	LDCW	0(%sr2,%r20), %r1			/* Barrier */
 #endif
 	stw	%r20, 0(%sr2,%r20)
 #if ENABLE_LWS_DEBUG
@@ -659,8 +658,7 @@ cas_action:
 	/* Error occurred on load or store */
 	/* Free lock */
 #ifdef CONFIG_SMP
-98:	LDCW	0(%sr2,%r20), %r1			/* Barrier */
-99:	ALTERNATIVE(98b, 99b, ALT_COND_NO_SMP, INSN_NOP)
+	LDCW	0(%sr2,%r20), %r1			/* Barrier */
 #endif
 	stw	%r20, 0(%sr2,%r20)
 #if ENABLE_LWS_DEBUG
@@ -864,8 +862,7 @@ cas2_action:
 cas2_end:
 	/* Free lock */
 #ifdef CONFIG_SMP
-98:	LDCW	0(%sr2,%r20), %r1			/* Barrier */
-99:	ALTERNATIVE(98b, 99b, ALT_COND_NO_SMP, INSN_NOP)
+	LDCW	0(%sr2,%r20), %r1			/* Barrier */
 #endif
 	stw	%r20, 0(%sr2,%r20)
 	/* Enable interrupts */
@@ -878,8 +875,7 @@ cas2_end:
 	/* Error occurred on load or store */
 	/* Free lock */
 #ifdef CONFIG_SMP
-98:	LDCW	0(%sr2,%r20), %r1			/* Barrier */
-99:	ALTERNATIVE(98b, 99b, ALT_COND_NO_SMP, INSN_NOP)
+	LDCW	0(%sr2,%r20), %r1			/* Barrier */
 #endif
 	stw	%r20, 0(%sr2,%r20)
 	ssm	PSW_SM_I, %r0