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Subject[PATCH 4/4] ARCv2: entry: Reduce perf intr return path
Date
In the more likely case of returning to kernel from perf interrupt, do a
fast path returning w/o bothering about CONFIG_PREEMPT etc

However, if returning to user space, need do go thru the usual gyrations,
as check for pending signals is an absolute must.

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
---
arch/arc/include/asm/entry-arcv2.h | 2 ++
arch/arc/kernel/entry-arcv2.S | 23 ++++++++++++++++++++++-
2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/arch/arc/include/asm/entry-arcv2.h b/arch/arc/include/asm/entry-arcv2.h
index 257a68f3c2fe..8b49b327b1f9 100644
--- a/arch/arc/include/asm/entry-arcv2.h
+++ b/arch/arc/include/asm/entry-arcv2.h
@@ -58,6 +58,8 @@
/*------------------------------------------------------------------------*/
.macro INTERRUPT_EPILOGUE called_from

+ ; Assumes STATUS32.Z bit set if return to K
+
.ifnc \called_from, exception
add sp, sp, 12 ; skip BTA/ECR/orig_r0 placeholderss
.endif
diff --git a/arch/arc/kernel/entry-arcv2.S b/arch/arc/kernel/entry-arcv2.S
index cc558a25b8fa..9ca1d146426b 100644
--- a/arch/arc/kernel/entry-arcv2.S
+++ b/arch/arc/kernel/entry-arcv2.S
@@ -51,7 +51,7 @@ VECTOR handle_interrupt ; (16) Timer0
VECTOR handle_interrupt ; unused (Timer1)
VECTOR handle_interrupt ; unused (WDT)
VECTOR handle_interrupt ; (19) Inter core Interrupt (IPI)
-VECTOR handle_interrupt ; (20) perf Interrupt
+VECTOR handle_interrupt_pct ; (20) perf Interrupt
VECTOR handle_interrupt ; (21) Software Triggered Intr (Self IPI)
VECTOR handle_interrupt ; unused
VECTOR handle_interrupt ; (23) unused
@@ -97,6 +97,26 @@ ENTRY(handle_interrupt)

END(handle_interrupt)

+ENTRY(handle_interrupt_pct)
+
+ INTERRUPT_PROLOGUE irq
+
+ IRQ_DISABLE
+
+ lr r0, [ICAUSE]
+
+ bl.d arch_do_IRQ
+ mov r1, sp
+
+ ld r0, [sp, PT_status32] ; returning to User/Kernel Mode
+ btst r0, STATUS_U_BIT
+ bnz resume_user_mode_begin
+
+ clri
+ b .Lisr_ret_fast_path_to_k
+
+END(handle_interrupt_pct)
+
;################### Non TLB Exception Handling #############################

ENTRY(EV_SWI)
@@ -224,6 +244,7 @@ debug_marker_l1:
bset.nz r11, r11, AUX_IRQ_ACT_BIT_U ; NZ means U
sr r11, [AUX_IRQ_ACT]

+.Lisr_ret_fast_path_to_k:
INTERRUPT_EPILOGUE irq
rtie

--
2.7.4
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