This adds the asm macro definition 'b_if_no_resched' that performs a conditional
branch depending on the preempt need_resched state.
Signed-off-by: Ard Biesheuvel <ard.biesheu...@linaro.org>
---
arch/arm64/include/asm/assembler.h | 21 +++++++++++++++++++++
1 file changed, 21 insertions(+)
diff --git a/arch/arm64/include/asm/assembler.h
b/arch/arm64/include/asm/assembler.h
index fd3e3924041b..296105fd3021 100644
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -22,6 +22,11 @@
#include <asm/ptrace.h>
+#if defined(CONFIG_PREEMPT) || defined(CONFIG_PREEMPT_VOLUNTARY)
+#include <asm/asm-offsets.h>
+#include <asm/thread_info.h>
+#endif
+
/*
* Stack pushing/popping (register pairs only). Equivalent to store decrement
* before, load increment after.
@@ -146,3 +151,19 @@ lr .req x30 // link register
#endif
orr \rd, \lbits, \hbits, lsl #32
.endm
+
+/*
+ * Branch to 'lb' but only if we have not been tagged for preemption.
+ *
+ * Expects current->thread_info in ti, or NULL if running in interrupt
+ * context. reg is a scratch x register.
+ */
+ .macro b_if_no_resched, ti, reg, lb
+#if defined(CONFIG_PREEMPT) || defined(CONFIG_PREEMPT_VOLUNTARY)
+ cbz \ti, \lb /* have thread_info? */
+ ldr \reg, [\ti, #TI_FLAGS] /* get flags */
+ tbz \reg, #TIF_NEED_RESCHED, \lb /* need rescheduling? */
+#else
+ b \lb
+#endif
+ .endm
--
1.8.3.2
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