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From: Egor Elchinov via Tarantool-patches <tarantool-patches@dev.tarantool.org>
To: gorcunov@tarantool.org, alyapunov@tarantool.org
Cc: tarantool-patches@dev.tarantool.org,
	Egor Elchinov <elchinov.es@gmail.com>
Subject: [Tarantool-patches] [PATCH v3 1/4] fiber: add PoC for fiber creation backtrace
Date: Wed, 14 Jul 2021 14:12:49 +0300
Message-ID: <fcf071b73c76b6900b1a9ab4b6931fb6578b5da3.1626260838.git.elchinov.es@gmail.com> (raw)
In-Reply-To: <cover.1626260838.git.elchinov.es@gmail.com>

From: Egor Elchinov <elchinov.es@gmail.com>

For now fiber creation backtrace is stored
in the separate subtable of fiber.info
called backtrace_parent for convenience.

Lua stacks of fiber creation
aren't preserved in backtrace yet because
of need to somehow handle parent Lua state
inside the child fiber for this sake.

Backtrace caching and demangling
aren't present yet too as this is a
proof-of-concept implementation.

Due to the limited libunwind API under osx for now
this patch uses backtrace() from <execinfo.h> and
dladdr() from <dlfcn.h> instead of absent
libunwind routines.

Custom backtrace() function was renamed to
backtrace_to_buf() because of the name conflict
with backtrace() routine from <execinfo.h>.

Needed for: #4002
---
 src/lib/core/backtrace.cc                     | 99 ++++++++++++++++++-
 src/lib/core/backtrace.h                      | 10 +-
 src/lib/core/crash.c                          |  2 +-
 src/lib/core/fiber.c                          |  8 ++
 src/lib/core/fiber.h                          | 16 +++
 src/lua/fiber.c                               | 10 ++
 .../gh-4002-fiber-creation-backtrace.result   | 57 +++++++++++
 .../gh-4002-fiber-creation-backtrace.test.lua | 27 +++++
 8 files changed, 225 insertions(+), 4 deletions(-)
 create mode 100644 test/app/gh-4002-fiber-creation-backtrace.result
 create mode 100644 test/app/gh-4002-fiber-creation-backtrace.test.lua

diff --git a/src/lib/core/backtrace.cc b/src/lib/core/backtrace.cc
index b4048089f..ef8a70f1b 100644
--- a/src/lib/core/backtrace.cc
+++ b/src/lib/core/backtrace.cc
@@ -46,6 +46,11 @@
 #ifdef ENABLE_BACKTRACE
 #include <libunwind.h>
 
+#ifdef TARGET_OS_DARWIN
+#include <execinfo.h>
+#include <dlfcn.h>
+#endif
+
 #include "small/region.h"
 #include "small/static.h"
 /*
@@ -131,7 +136,7 @@ error:
 }
 
 char *
-backtrace(char *start, size_t size)
+backtrace_to_buf(char *start, size_t size)
 {
 	int frame_no = 0;
 	unw_word_t sp = 0, old_sp = 0, ip, offset;
@@ -432,11 +437,101 @@ out:
 	free(demangle_buf);
 }
 
+/**
+ * Collect up to `limit' IP register values
+ * for frames of the current stack into `ip_buf'.
+ * Must be by far faster than usual backtrace according to the
+ * libunwind doc for unw_backtrace().
+ */
+void NOINLINE
+backtrace_collect_ip(void **ip_buf, int limit)
+{
+	memset(ip_buf, 0, limit * sizeof(*ip_buf));
+#ifndef TARGET_OS_DARWIN
+	unw_backtrace(ip_buf, limit);
+#else
+	backtrace(ip_buf, limit);
+#endif
+}
+
+/**
+ * Call `cb' callback for not more than
+ * first `limit' frames present in the `ip_buf'.
+ *
+ * The implementation uses poorly documented `get_proc_name' callback
+ * from the `unw_accessors_t' to get procedure names via `ip_buf' values.
+ * Although `get_proc_name' is present on most architectures, it's an optional
+ * field, so procedure name is allowed to be absent (NULL) in `cb' call.
+ *
+ * TODO: to add cache and demangling support
+ */
+void
+backtrace_foreach_ip(backtrace_cb cb, void **ip_buf, int limit,
+		     void *cb_ctx)
+{
+#ifndef TARGET_OS_DARWIN
+	char proc_name[BACKTRACE_NAME_MAX];
+	unw_word_t ip = 0, offset = 0;
+	unw_proc_info_t pi;
+	int frame_no, ret = 0;
+	char *proc = NULL;
+
+	unw_accessors_t *acc = unw_get_accessors(unw_local_addr_space);
+
+	/*
+	 * RIPs collecting comes from inside a helper routine
+	 * so we skip the collector function address itself thus
+	 * start fetching functions with frame number = 1.
+	 */
+	for (frame_no = 1; frame_no < limit && ip_buf[frame_no] != NULL;
+	     frame_no++) {
+		ip = (unw_word_t)ip_buf[frame_no];
+
+		if (acc->get_proc_name == NULL) {
+			ret = unw_get_proc_info_by_ip(unw_local_addr_space,
+						      ip, &pi, NULL);
+			offset = ip - pi.start_ip;
+		} else {
+			ret = acc->get_proc_name(unw_local_addr_space, ip,
+						 proc_name, sizeof(proc_name),
+						 &offset, NULL);
+			proc = proc_name;
+		}
+		if (ret != 0 || cb(frame_no - 1, (void *)ip, proc,
+				   (size_t)offset, cb_ctx) != 0)
+			break;
+	}
+
+	if (ret != 0)
+		say_debug("unwinding error: %s", unw_strerror(ret));
+#else
+	int frame_no, ret = 1;
+	void *ip = NULL;
+	size_t offset = 0;
+	Dl_info dli;
+
+	for (frame_no = 1; frame_no < limit && ip_buf[frame_no] != NULL;
+	     ++frame_no) {
+		ip = ip_buf[frame_no];
+		ret = dladdr(ip, &dli);
+		if (ret == 0)
+			break;
+		offset = (char *)ip - (char *)dli.dli_saddr;
+
+		if (cb(frame_no - 1, ip, dli.dli_sname, offset, cb_ctx) != 0)
+			break;
+	}
+
+	if (ret == 0)
+		say_debug("unwinding error: %i", ret);
+#endif
+}
+
 void
 print_backtrace(void)
 {
 	char *start = (char *)static_alloc(SMALL_STATIC_SIZE);
-	fdprintf(STDERR_FILENO, "%s", backtrace(start, SMALL_STATIC_SIZE));
+	fdprintf(STDERR_FILENO, "%s", backtrace_to_buf(start, SMALL_STATIC_SIZE));
 }
 #endif /* ENABLE_BACKTRACE */
 
diff --git a/src/lib/core/backtrace.h b/src/lib/core/backtrace.h
index e0ae56be4..4552c14e1 100644
--- a/src/lib/core/backtrace.h
+++ b/src/lib/core/backtrace.h
@@ -31,6 +31,7 @@
  * SUCH DAMAGE.
  */
 #include "trivia/config.h"
+#include "trivia/util.h"
 #include <stddef.h>
 
 #if defined(__cplusplus)
@@ -41,7 +42,7 @@ extern "C" {
 #include <coro.h>
 
 char *
-backtrace(char *start, size_t size);
+backtrace_to_buf(char *start, size_t size);
 
 void print_backtrace(void);
 
@@ -55,6 +56,13 @@ backtrace_foreach(backtrace_cb cb, coro_context *coro_ctx, void *cb_ctx);
 void
 backtrace_proc_cache_clear(void);
 
+void NOINLINE
+backtrace_collect_ip(void **ip_buf, int limit);
+
+void
+backtrace_foreach_ip(backtrace_cb cb, void **ip_buf, int limit,
+		     void *cb_ctx);
+
 #endif /* ENABLE_BACKTRACE */
 
 #if defined(__cplusplus)
diff --git a/src/lib/core/crash.c b/src/lib/core/crash.c
index abb7837e6..d1990d68b 100644
--- a/src/lib/core/crash.c
+++ b/src/lib/core/crash.c
@@ -213,7 +213,7 @@ crash_collect(int signo, siginfo_t *siginfo, void *ucontext)
 
 #ifdef ENABLE_BACKTRACE
 	char *start = cinfo->backtrace_buf;
-	backtrace(start, sizeof(cinfo->backtrace_buf));
+	backtrace_to_buf(start, sizeof(cinfo->backtrace_buf));
 #endif
 
 #ifdef HAS_GREG
diff --git a/src/lib/core/fiber.c b/src/lib/core/fiber.c
index 759c7da6a..924ff3c82 100644
--- a/src/lib/core/fiber.c
+++ b/src/lib/core/fiber.c
@@ -45,6 +45,11 @@
 
 extern void cord_on_yield(void);
 
+#if ENABLE_BACKTRACE
+#include "backtrace.h" /* fast_trace */
+
+#endif /* ENABLE_BACKTRACE */
+
 #if ENABLE_FIBER_TOP
 #include <x86intrin.h> /* __rdtscp() */
 
@@ -1259,6 +1264,9 @@ fiber_new_ex(const char *name, const struct fiber_attr *fiber_attr,
 	fiber->f = f;
 	fiber->fid = cord->next_fid;
 	fiber_set_name(fiber, name);
+#if ENABLE_BACKTRACE
+	backtrace_collect_ip(fiber->parent_bt_ip_buf, FIBER_PARENT_BT_MAX);
+#endif /* ENABLE_BACKTRACE */
 	register_fid(fiber);
 	fiber->csw = 0;
 
diff --git a/src/lib/core/fiber.h b/src/lib/core/fiber.h
index 8f4e14796..beed58866 100644
--- a/src/lib/core/fiber.h
+++ b/src/lib/core/fiber.h
@@ -111,6 +111,18 @@ struct cpu_stat {
 
 #endif /* ENABLE_FIBER_TOP */
 
+#if ENABLE_BACKTRACE
+
+enum {
+	/**
+	 * Maximum entries count to grab
+	 * from the fiber creation backtrace.
+	 */
+	FIBER_PARENT_BT_MAX = 8
+};
+
+#endif /* ENABLE_BACKTRACE */
+
 enum {
 	/** Both limits include terminating 0. */
 	FIBER_NAME_INLINE = 40,
@@ -640,6 +652,10 @@ struct fiber {
 	 */
 	char *name;
 	char inline_name[FIBER_NAME_INLINE];
+#if ENABLE_BACKTRACE
+	/** Fiber creation backtrace chunk. */
+	void *parent_bt_ip_buf[FIBER_PARENT_BT_MAX];
+#endif /* ENABLE_BACKTRACE */
 };
 
 /** Invoke on_stop triggers and delete them. */
diff --git a/src/lua/fiber.c b/src/lua/fiber.c
index 91898c283..7b21361d4 100644
--- a/src/lua/fiber.c
+++ b/src/lua/fiber.c
@@ -308,6 +308,16 @@ lbox_fiber_statof_map(struct fiber *f, void *cb_ctx, bool backtrace)
 		backtrace_foreach(fiber_backtrace_cb,
 				  f != fiber() ? &f->ctx : NULL, &tb_ctx);
 		lua_settable(L, -3);
+
+		tb_ctx.lua_frame = 0;
+		tb_ctx.tb_frame = 0;
+		tb_ctx.R = NULL;
+		lua_pushstring(L, "backtrace_parent");
+		lua_newtable(L);
+		backtrace_foreach_ip(fiber_backtrace_cb,
+				     f->parent_bt_ip_buf,
+				     FIBER_PARENT_BT_MAX, &tb_ctx);
+		lua_settable(L, -3);
 #endif /* ENABLE_BACKTRACE */
 	}
 	return 0;
diff --git a/test/app/gh-4002-fiber-creation-backtrace.result b/test/app/gh-4002-fiber-creation-backtrace.result
new file mode 100644
index 000000000..4934b82d6
--- /dev/null
+++ b/test/app/gh-4002-fiber-creation-backtrace.result
@@ -0,0 +1,57 @@
+-- test-run result file version 2
+yaml = require('yaml')
+ | ---
+ | ...
+fiber = require('fiber')
+ | ---
+ | ...
+test_run = require('test_run').new()
+ | ---
+ | ...
+
+local stack_len = 0
+ | ---
+ | ...
+local parent_stack_len = 0
+ | ---
+ | ...
+
+test_run:cmd('setopt delimiter ";"')
+ | ---
+ | - true
+ | ...
+foo = function()
+    local id = fiber.self():id()
+    local info = fiber.info()[id]
+    local stack = info.backtrace
+    stack_len = stack and #stack or -1
+    local parent_stack = info.backtrace_parent
+    parent_stack_len = parent_stack and #parent_stack or -1
+end;
+ | ---
+ | ...
+
+test_run:cmd('setopt delimiter ""');
+ | ---
+ | - true
+ | ...
+
+local bar,baz
+ | ---
+ | ...
+
+bar = function(n) if n ~= 0 then baz(n-1) else fiber.create(foo) end end
+ | ---
+ | ...
+baz = function(n) bar(n) end
+ | ---
+ | ...
+
+baz(10)
+ | ---
+ | ...
+assert(parent_stack_len > 0 or stack_len == -1)
+ | ---
+ | - true
+ | ...
+
diff --git a/test/app/gh-4002-fiber-creation-backtrace.test.lua b/test/app/gh-4002-fiber-creation-backtrace.test.lua
new file mode 100644
index 000000000..24d41a860
--- /dev/null
+++ b/test/app/gh-4002-fiber-creation-backtrace.test.lua
@@ -0,0 +1,27 @@
+yaml = require('yaml')
+fiber = require('fiber')
+test_run = require('test_run').new()
+
+local stack_len = 0
+local parent_stack_len = 0
+
+test_run:cmd('setopt delimiter ";"')
+foo = function()
+    local id = fiber.self():id()
+    local info = fiber.info()[id]
+    local stack = info.backtrace
+    stack_len = stack and #stack or -1
+    local parent_stack = info.backtrace_parent
+    parent_stack_len = parent_stack and #parent_stack or -1
+end;
+
+test_run:cmd('setopt delimiter ""');
+
+local bar,baz
+
+bar = function(n) if n ~= 0 then baz(n-1) else fiber.create(foo) end end
+baz = function(n) bar(n) end
+
+baz(10)
+assert(parent_stack_len > 0 or stack_len == -1)
+
-- 
2.31.1


  reply	other threads:[~2021-07-14 11:14 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-14 11:12 [Tarantool-patches] [PATCH v3 0/4] fiber: introduce " Egor Elchinov via Tarantool-patches
2021-07-14 11:12 ` Egor Elchinov via Tarantool-patches [this message]
2021-07-14 11:12 ` [Tarantool-patches] [PATCH v3 2/4] fiber: add option and PoC for Lua parent backtrace Egor Elchinov via Tarantool-patches
2021-07-14 11:12 ` [Tarantool-patches] [PATCH v3 3/4] fiber: refactor lua backtrace routines Egor Elchinov via Tarantool-patches
2021-07-14 11:12 ` [Tarantool-patches] [PATCH v3 4/4] fiber: refactor C backtrace and add changelog Egor Elchinov via Tarantool-patches
2021-07-16  6:12 ` [Tarantool-patches] [PATCH v3 0/4] fiber: introduce creation backtrace Cyrill Gorcunov via Tarantool-patches
2021-07-27 11:53 ` Vladimir Davydov via Tarantool-patches

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