From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Sun, 16 Oct 2016 06:22:56 +0000 (+0200)
Subject: Restartable sequences: don't clear rseq_cs after c.s.
X-Git-Url: http://git.efficios.com/?p=deliverable%2Flinux.git;a=commitdiff_plain;h=06f70f3d671019d8b8b2c6937f8f5834cb7e7118

Restartable sequences: don't clear rseq_cs after c.s.

We can remove this rseq_cs=NULL clearing step at the end of the critical
section, since the kernel checks for lower and upper address ranges when
it preempts or delivers a signals. The kernel will either take care of
clearing it at the next preemption or signal delivery, or the next
critical section will either change its value, or set it to the same
value.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---

diff --git a/tools/testing/selftests/rseq/rseq-arm.h b/tools/testing/selftests/rseq/rseq-arm.h
index a8af6def22e7..b5f57d250071 100644
--- a/tools/testing/selftests/rseq/rseq-arm.h
+++ b/tools/testing/selftests/rseq/rseq-arm.h
@@ -47,11 +47,6 @@ do {									\
 /*
  * The __rseq_table section can be used by debuggers to better handle
  * single-stepping through the restartable critical sections.
- *
- * Load the immediate value 0 into register r1 right after the ldr
- * instruction to improve instruction-level parallelism: load the
- * constant while the processor is stalled waiting for the load to
- * complete, which is required by the following comparison and branch.
  */
 
 #define RSEQ_FINISH_ASM(_target_final, _to_write_final, _start_value, \
@@ -72,7 +67,6 @@ do { \
 		"str r0, [%[rseq_cs]]\n\t" \
 		RSEQ_INJECT_ASM(2) \
 		"ldr r0, %[current_event_counter]\n\t" \
-		"mov r1, #0\n\t" \
 		"cmp %[start_event_counter], r0\n\t" \
 		"bne 5f\n\t" \
 		RSEQ_INJECT_ASM(3) \
@@ -80,15 +74,12 @@ do { \
 		_final_store \
 		"2:\n\t" \
 		RSEQ_INJECT_ASM(5) \
-		"str r1, [%[rseq_cs]]\n\t" \
 		_teardown \
 		"b 4f\n\t" \
 		".balign 32\n\t" \
 		"3:\n\t" \
 		".word 1b, 0x0, 2b, 0x0, 5f, 0x0, 0x0, 0x0\n\t" \
 		"5:\n\t" \
-		"mov r1, #0\n\t" \
-		"str r1, [%[rseq_cs]]\n\t" \
 		_teardown \
 		"b %l[failure]\n\t" \
 		"4:\n\t" \
@@ -99,7 +90,7 @@ do { \
 		  _spec_input \
 		  _final_input \
 		  RSEQ_INJECT_INPUT \
-		: "r0", "r1", "memory", "cc" \
+		: "r0", "memory", "cc" \
 		  _extra_clobber \
 		  RSEQ_INJECT_CLOBBER \
 		: _failure \
diff --git a/tools/testing/selftests/rseq/rseq-ppc.h b/tools/testing/selftests/rseq/rseq-ppc.h
index 287ab75ca77b..29498b559d66 100644
--- a/tools/testing/selftests/rseq/rseq-ppc.h
+++ b/tools/testing/selftests/rseq/rseq-ppc.h
@@ -86,13 +86,9 @@ do {									\
 		_final_store \
 		"2:\n\t" \
 		RSEQ_INJECT_ASM(5) \
-		"li %%r17, 0\n\t" \
-		"std %%r17, 0(%[rseq_cs])\n\t" \
 		_teardown \
 		"b 5f\n\t" \
 		"4:\n\t" \
-		"li %%r17, 0\n\t" \
-		"std %%r17, 0(%[rseq_cs])\n\t" \
 		_teardown \
 		"b %l[failure]\n\t" \
 		"5:\n\t" \
@@ -192,13 +188,9 @@ do {									\
 		_final_store \
 		"2:\n\t" \
 		RSEQ_INJECT_ASM(5) \
-		"li %%r17, 0\n\t" \
-		"stw %%r17, 0(%[rseq_cs])\n\t" \
 		_teardown \
 		"b 5f\n\t" \
 		"4:\n\t" \
-		"li %%r17, 0\n\t" \
-		"stw %%r17, 0(%[rseq_cs])\n\t" \
 		_teardown \
 		"b %l[failure]\n\t" \
 		"5:\n\t" \
diff --git a/tools/testing/selftests/rseq/rseq-x86.h b/tools/testing/selftests/rseq/rseq-x86.h
index 9dab0946a35a..f5a792a16963 100644
--- a/tools/testing/selftests/rseq/rseq-x86.h
+++ b/tools/testing/selftests/rseq/rseq-x86.h
@@ -75,11 +75,9 @@ do { \
 		_final_store \
 		"2:\n\t" \
 		RSEQ_INJECT_ASM(5) \
-		"movq $0, %[rseq_cs]\n\t" \
 		_teardown \
 		".pushsection __rseq_failure, \"a\"\n\t" \
 		"4:\n\t" \
-		"movq $0, %[rseq_cs]\n\t" \
 		_teardown \
 		"jmp %l[failure]\n\t" \
 		".popsection\n\t" \
@@ -219,11 +217,9 @@ do { \
 		_final_store \
 		"2:\n\t" \
 		RSEQ_INJECT_ASM(5) \
-		"movl $0, %[rseq_cs]\n\t" \
 		_teardown \
 		".pushsection __rseq_failure, \"a\"\n\t" \
 		"4:\n\t" \
-		"movl $0, %[rseq_cs]\n\t" \
 		_teardown \
 		"jmp %l[failure]\n\t" \
 		".popsection\n\t" \