[PATCH resend 1/8] unwind: lift up unw_flush_cache from mmap cache management code

[Masatake YAMATO]

For making mmap cache code reusable from other areas in strace
than unwind, mmap cache related code and unwind related code
should be separated.

This change is one of the steps for the separation. It moves
unw_flush_cache function call from the core of mmap cache code
to upper level code.

* unwind.c (MMAP_CACHE_REBUILD_*): New enum.
(rebuild_cache_if_invalid): Return MMAP_CACHE_REBUILD_* instead of
bool value.
(build_mmap_cache): Don't call unw_flush_cache here.
(unwind_print_stacktrace, unwind_capture_stacktrace): Call
unw_flush_cache here instead.

Signed-off-by: Masatake YAMATO <yamato at redhat.com>
---
 unwind.c | 44 +++++++++++++++++++++++++++++++++++---------
 1 file changed, 35 insertions(+), 9 deletions(-)

diff --git a/unwind.c b/unwind.c
index ecda1842..c171844c 100644
--- a/unwind.c
+++ b/unwind.c
@@ -154,8 +154,6 @@ build_mmap_cache(struct tcb *tcp)
 	char filename[sizeof("/proc/4294967296/maps")];
 	char buffer[PATH_MAX + 80];
 
-	unw_flush_cache(libunwind_as, 0, 0);
-
 	xsprintf(filename, "/proc/%u/maps", tcp->pid);
 	fp = fopen_for_input(filename, "r");
 	if (!fp) {
@@ -247,17 +245,29 @@ delete_mmap_cache(struct tcb *tcp, const char *caller)
 	tcp->mmap_cache_size = 0;
 }
 
-static bool
+enum mmap_cache_rebuild_result {
+	MMAP_CACHE_REBUILD_NOCACHE,
+	MMAP_CACHE_REBUILD_READY,
+	MMAP_CACHE_REBUILD_RENEWED,
+};
+
+static enum mmap_cache_rebuild_result
 rebuild_cache_if_invalid(struct tcb *tcp, const char *caller)
 {
+	enum mmap_cache_rebuild_result r = MMAP_CACHE_REBUILD_READY;
 	if ((tcp->mmap_cache_generation != mmap_cache_generation)
 	    && tcp->mmap_cache)
 		delete_mmap_cache(tcp, caller);
 
-	if (!tcp->mmap_cache)
+	if (!tcp->mmap_cache) {
+		r = MMAP_CACHE_REBUILD_RENEWED;
 		build_mmap_cache(tcp);
+	}
+
+	if (!(tcp->mmap_cache && tcp->mmap_cache_size))
+		r = MMAP_CACHE_REBUILD_NOCACHE;
 
-	return tcp->mmap_cache && tcp->mmap_cache_size;
+	return r;
 }
 
 void
@@ -578,9 +588,17 @@ unwind_print_stacktrace(struct tcb *tcp)
 	if (tcp->queue->head) {
 		debug_func_msg("head: tcp=%p, queue=%p", tcp, tcp->queue->head);
 		queue_print(tcp->queue);
-	} else if (rebuild_cache_if_invalid(tcp, __func__)) {
-		debug_func_msg("walk: tcp=%p, queue=%p", tcp, tcp->queue->head);
-		stacktrace_walk(tcp, print_call_cb, print_error_cb, NULL);
+	} else switch (rebuild_cache_if_invalid(tcp, __func__)) {
+		case MMAP_CACHE_REBUILD_RENEWED:
+			unw_flush_cache(libunwind_as, 0, 0);
+			/* Fall through */
+		case MMAP_CACHE_REBUILD_READY:
+			debug_func_msg("walk: tcp=%p, queue=%p", tcp, tcp->queue->head);
+			stacktrace_walk(tcp, print_call_cb, print_error_cb, NULL);
+			break;
+		default:
+			/* Do nothing */
+			;
 	}
 }
 
@@ -599,9 +617,17 @@ unwind_capture_stacktrace(struct tcb *tcp)
 	if (tcp->queue->head)
 		error_msg_and_die("bug: unprinted entries in queue");
 
-	if (rebuild_cache_if_invalid(tcp, __func__)) {
+	switch (rebuild_cache_if_invalid(tcp, __func__)) {
+	case MMAP_CACHE_REBUILD_RENEWED:
+		unw_flush_cache(libunwind_as, 0, 0);
+		/* Fall through */
+	case MMAP_CACHE_REBUILD_READY:
 		stacktrace_walk(tcp, queue_put_call, queue_put_error,
 				tcp->queue);
 		debug_func_msg("tcp=%p, queue=%p", tcp, tcp->queue->head);
+		break;
+	default:
+		/* Do nothing */
+		;
 	}
 }
-- 
2.14.3