ARM: 9480/1: entry: expand comment in __switch_tografted

As per discussion between the developers in the mail thread
linked, expand the comment in __switch_to so that readers
of the code understand what is going on.

Suggested-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Linus Walleij <linusw@kernel.org>>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>

1 files changed, 49 insertions, 0 deletions

diff --git a/tools/perf/tests/perf-hooks.c b/tools/perf/tests/perf-hooks.c
new file mode 100644
index 000000000..78cdeb896
--- /dev/null
+++ b/tools/perf/tests/perf-hooks.c
@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <signal.h>
+#include <stdlib.h>
+
+#include "tests.h"
+#include "debug.h"
+#include "perf-hooks.h"
+
+static void sigsegv_handler(int sig __maybe_unused)
+{
+	pr_debug("SIGSEGV is observed as expected, try to recover.\n");
+	perf_hooks__recover();
+	signal(SIGSEGV, SIG_DFL);
+	raise(SIGSEGV);
+	exit(-1);
+}
+
+
+static void the_hook(void *_hook_flags)
+{
+	int *hook_flags = _hook_flags;
+
+	*hook_flags = 1234;
+
+	/* Generate a segfault, test perf_hooks__recover */
+	raise(SIGSEGV);
+}
+
+static int test__perf_hooks(struct test_suite *test __maybe_unused, int subtest __maybe_unused)
+{
+	int hook_flags = 0;
+
+	signal(SIGSEGV, sigsegv_handler);
+	perf_hooks__set_hook("test", the_hook, &hook_flags);
+	perf_hooks__invoke_test();
+
+	/* hook is triggered? */
+	if (hook_flags != 1234) {
+		pr_debug("Setting failed: %d (%p)\n", hook_flags, &hook_flags);
+		return TEST_FAIL;
+	}
+
+	/* the buggy hook is removed? */
+	if (perf_hooks__get_hook("test"))
+		return TEST_FAIL;
+	return TEST_OK;
+}
+
+DEFINE_SUITE("perf hooks", perf_hooks);