[Tarantool-patches] [PATCH v2 1/1] fiber: extend max fiber name length to 255

[Vladislav Shpilevoy <v.shpilevoy@tarantool.org>]

Users keep complaining about too short fiber name. New limit is
255, should be enough for any sane name.

Closes #4394

@TarantoolBot document
Title: fiber.name length limit.

It was 32, now it is 255. Besides, it seems like `fiber.name`
`{truncate = true}` option is not documented.

By default, if a new name is too long, `fiber.name(new_name)`
fails with an exception. To make it always succeed there is an
option 'truncate': `fiber.name(new_name, {truncate = true})`. It
truncates the name to the max length if it is too long.
---
Branch: http://github.com/tarantool/tarantool/tree/gerold103/gh-4394-fiber-name-inline
Issue: https://github.com/tarantool/tarantool/issues/4394

Changes in v2:
- Short fiber names are kept inside struct fiber.

 src/lib/core/fiber.c    | 28 ++++++++++++++++++++++++++--
 src/lib/core/fiber.h    | 14 +++++++++++---
 test/app/fiber.result   |  8 ++++----
 test/app/fiber.test.lua |  2 +-
 test/unit/fiber.cc      |  6 +++---
 test/unit/fiber.result  |  2 +-
 6 files changed, 46 insertions(+), 14 deletions(-)

diff --git a/src/lib/core/fiber.c b/src/lib/core/fiber.c
index ada7972cb..359ef1187 100644
--- a/src/lib/core/fiber.c
+++ b/src/lib/core/fiber.c
@@ -912,8 +912,26 @@ fiber_loop(MAYBE_UNUSED void *data)
 void
 fiber_set_name(struct fiber *fiber, const char *name)
 {
-	assert(name != NULL);
-	snprintf(fiber->name, sizeof(fiber->name), "%s", name);
+	size_t len = strlen(name);
+	if (len <= FIBER_NAME_INLINE) {
+		if (fiber->name != fiber->inline_name) {
+			free(fiber->name);
+			fiber->name = fiber->inline_name;
+		}
+	} else {
+		if (len > FIBER_NAME_MAX)
+			len = FIBER_NAME_MAX;
+		char *new_name;
+		if (fiber->name != fiber->inline_name)
+			new_name = realloc(fiber->name, len + 1);
+		else
+			new_name = malloc(len + 1);
+		if (new_name == NULL)
+			panic("fiber_set_name() failed with OOM");
+		fiber->name = new_name;
+	}
+	memcpy(fiber->name, name, len);
+	fiber->name[len] = 0;
 }
 
 static inline void *
@@ -1242,6 +1260,9 @@ fiber_destroy(struct cord *cord, struct fiber *f)
 	region_destroy(&f->gc);
 	fiber_stack_destroy(f, &cord->slabc);
 	diag_destroy(&f->diag);
+	if (f->name != f->inline_name)
+		free(f->name);
+	f->name = NULL;
 }
 
 void
@@ -1357,6 +1378,7 @@ cord_create(struct cord *cord, const char *name)
 	fiber_reset(&cord->sched);
 	diag_create(&cord->sched.diag);
 	region_create(&cord->sched.gc, &cord->slabc);
+	cord->sched.name = NULL;
 	fiber_set_name(&cord->sched, "sched");
 	cord->fiber = &cord->sched;
 
@@ -1405,6 +1427,8 @@ cord_destroy(struct cord *cord)
 	}
 	region_destroy(&cord->sched.gc);
 	diag_destroy(&cord->sched.diag);
+	if (cord->sched.name != cord->sched.inline_name)
+		free(cord->sched.name);
 	slab_cache_destroy(&cord->slabc);
 }
 
diff --git a/src/lib/core/fiber.h b/src/lib/core/fiber.h
index 8a3e5aef5..fedc37c87 100644
--- a/src/lib/core/fiber.h
+++ b/src/lib/core/fiber.h
@@ -111,7 +111,10 @@ struct cpu_stat {
 
 #endif /* ENABLE_FIBER_TOP */
 
-enum { FIBER_NAME_MAX = 32 };
+enum {
+	FIBER_NAME_INLINE = 32,
+	FIBER_NAME_MAX = 255
+};
 
 /**
  * Fiber ids [0; 100] are reserved.
@@ -510,7 +513,12 @@ struct fiber {
 	struct ipc_wait_pad *wait_pad;
 	/** Exception which caused this fiber's death. */
 	struct diag diag;
-	char name[FIBER_NAME_MAX + 1];
+	/**
+	 * Name points at inline_name in case it is short. Long
+	 * name is allocated on the heap.
+	 */
+	char *name;
+	char inline_name[FIBER_NAME_INLINE + 1];
 };
 
 /** Invoke on_stop triggers and delete them. */
@@ -578,7 +586,7 @@ struct cord {
 	struct slab_cache slabc;
 	/** The "main" fiber of this cord, the scheduler. */
 	struct fiber sched;
-	char name[FIBER_NAME_MAX];
+	char name[FIBER_NAME_INLINE + 1];
 };
 
 extern __thread struct cord *cord_ptr;
diff --git a/test/app/fiber.result b/test/app/fiber.result
index 6d9604ad8..7331f61b3 100644
--- a/test/app/fiber.result
+++ b/test/app/fiber.result
@@ -1186,7 +1186,7 @@ fiber = nil
 ---
 ...
 --
--- gh-2622, gh-4011: fiber.name() truncates new name.
+-- gh-2622, gh-4011, gh-4394: fiber.name() truncates new name.
 --
 fiber = require('fiber')
 ---
@@ -1214,14 +1214,14 @@ fiber.name(long_name, {truncate = true})
 ...
 fiber.name()
 ---
-- aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+- aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
 ...
 f = fiber.self()
 ---
 ...
 fiber.name(f)
 ---
-- aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+- aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
 ...
 fiber.name(f, 'new_name')
 ---
@@ -1239,7 +1239,7 @@ fiber.name(f, long_name, {truncate = true})
 ...
 fiber.name(f)
 ---
-- aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+- aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
 ...
 --
 -- gh-3493 fiber.create() does not roll back memtx transaction
diff --git a/test/app/fiber.test.lua b/test/app/fiber.test.lua
index 6df210d9c..b8e9abc6e 100644
--- a/test/app/fiber.test.lua
+++ b/test/app/fiber.test.lua
@@ -504,7 +504,7 @@ test_run:cmd("setopt delimiter ''");
 fiber = nil
 
 --
--- gh-2622, gh-4011: fiber.name() truncates new name.
+-- gh-2622, gh-4011, gh-4394: fiber.name() truncates new name.
 --
 fiber = require('fiber')
 long_name = string.rep('a', 300)
diff --git a/test/unit/fiber.cc b/test/unit/fiber.cc
index 91f7d43f9..b0dfc9b14 100644
--- a/test/unit/fiber.cc
+++ b/test/unit/fiber.cc
@@ -171,9 +171,9 @@ fiber_name_test()
 
 	note("set new fiber name: %s.\n", fiber_name(fiber()));
 
-	const char *long_name = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
-		"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"\
-		"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";
+	char long_name[FIBER_NAME_MAX + 30];
+	memset(long_name, 'a', sizeof(long_name));
+	long_name[sizeof(long_name) - 1] = 0;
 
 	fiber_set_name(fiber(), long_name);
 
diff --git a/test/unit/fiber.result b/test/unit/fiber.result
index 7c9f85dcd..a61e0a2b8 100644
--- a/test/unit/fiber.result
+++ b/test/unit/fiber.result
@@ -5,7 +5,7 @@ SystemError Failed to allocate 42 bytes in allocator for exception: Cannot alloc
 
 # set new fiber name: Horace.
 
-# fiber name is truncated: aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa.
+# fiber name is truncated: aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa.
 
 	*** fiber_name_test: done ***
 	*** fiber_join_test ***
-- 
2.21.1 (Apple Git-122.3)