linux-kernel - [PATCH 4.19 15/47] Revert "arm64: preempt: Fix big-endian when checking preempt count in assembly"

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Date:   Thu, 19 Dec 2019 19:34:29 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>,
        Will Deacon <will@...nel.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Kevin Hilman <khilman@...libre.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 15/47] Revert "arm64: preempt: Fix big-endian when checking preempt count in assembly"

From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

This reverts commit 64694b276d74c653051637caa4bfa5e8c27b30ad which is
commit 7faa313f05cad184e8b17750f0cbe5216ac6debb upstream.

Turns out one of the pre-requsite patches wasn't in 4.19.y, so this
patch didn't make sense.  So let's revert it.

Reported-by: Steven Rostedt <rostedt@...dmis.org>
Reported-by: Will Deacon <will@...nel.org>
Cc: Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc: Kevin Hilman <khilman@...libre.com>
Cc: Sasha Levin <sashal@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/arm64/include/asm/assembler.h |    8 +++++---
 arch/arm64/kernel/entry.S          |    6 ++++--
 2 files changed, 9 insertions(+), 5 deletions(-)

--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -683,9 +683,11 @@ USER(\label, ic	ivau, \tmp2)			// invali
 	.macro		if_will_cond_yield_neon
 #ifdef CONFIG_PREEMPT
 	get_thread_info	x0
-	ldr		x0, [x0, #TSK_TI_PREEMPT]
-	sub		x0, x0, #PREEMPT_DISABLE_OFFSET
-	cbz		x0, .Lyield_\@
+	ldr		w1, [x0, #TSK_TI_PREEMPT]
+	ldr		x0, [x0, #TSK_TI_FLAGS]
+	cmp		w1, #PREEMPT_DISABLE_OFFSET
+	csel		x0, x0, xzr, eq
+	tbnz		x0, #TIF_NEED_RESCHED, .Lyield_\@	// needs rescheduling?
 	/* fall through to endif_yield_neon */
 	.subsection	1
 .Lyield_\@ :
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -622,8 +622,10 @@ el1_irq:
 	irq_handler
 
 #ifdef CONFIG_PREEMPT
-	ldr	x24, [tsk, #TSK_TI_PREEMPT]	// get preempt count
-	cbnz	x24, 1f				// preempt count != 0
+	ldr	w24, [tsk, #TSK_TI_PREEMPT]	// get preempt count
+	cbnz	w24, 1f				// preempt count != 0
+	ldr	x0, [tsk, #TSK_TI_FLAGS]	// get flags
+	tbz	x0, #TIF_NEED_RESCHED, 1f	// needs rescheduling?
 	bl	el1_preempt
 1:
 #endif