[Tarantool-patches] [PATCH v2] core: handle fiber cancellation for fiber.cond

[sergos@tarantool.org]

From: Sergey Ostanevich <sergos@tarantool.org>

Hi!

Thanks to Oleg Babin's comment I found there's no need to update any lua
interfaces, since the reason was in C implementation. Also, there is one
place the change is played, so after I fixed it I got complete testing 
pass. 
Force-pushed branch, v2 patch attached.



Before this patch fiber.cond():wait() just returns for cancelled
fiber. In contrast fiber.channel():get() threw "fiber is
canceled" error.
This patch unify behaviour of channels and condvars and also fixes
related net.box module problem - it was impossible to interrupt
net.box call with fiber.cancel because it used fiber.cond under
the hood. Test cases for both bugs are added.

Closes #4834
Closes #5013

Co-authored-by: Oleg Babin <olegrok@tarantool.org>

@TarantoolBot document
Title: fiber.cond():wait() throws if fiber is cancelled

Currently fiber.cond():wait() throws an error if waiting fiber is
cancelled like in case with fiber.channel():get().
---

Github: https://gitlab.com/tarantool/tarantool/-/commits/sergos/gh-5013-fiber-cond                                                                                                                          
Issue: https://github.com/tarantool/tarantool/issues/5013                                                                                                                                                   

 src/box/box.cc                                |  6 +-
 src/lib/core/fiber_cond.c                     |  1 +
 test/app-tap/gh-5013-fiber-cancel.test.lua    | 23 +++++++
 test/box/net.box_fiber_cancel_gh-4834.result  | 65 +++++++++++++++++++
 .../box/net.box_fiber_cancel_gh-4834.test.lua | 29 +++++++++
 5 files changed, 120 insertions(+), 4 deletions(-)
 create mode 100755 test/app-tap/gh-5013-fiber-cancel.test.lua
 create mode 100644 test/box/net.box_fiber_cancel_gh-4834.result
 create mode 100644 test/box/net.box_fiber_cancel_gh-4834.test.lua

diff --git a/src/box/box.cc b/src/box/box.cc
index 18568df3b..bfa1051f9 100644
--- a/src/box/box.cc
+++ b/src/box/box.cc
@@ -305,10 +305,8 @@ box_wait_ro(bool ro, double timeout)
 {
 	double deadline = ev_monotonic_now(loop()) + timeout;
 	while (is_box_configured == false || box_is_ro() != ro) {
-		if (fiber_cond_wait_deadline(&ro_cond, deadline) != 0)
-			return -1;
-		if (fiber_is_cancelled()) {
-			diag_set(FiberIsCancelled);
+		if (fiber_cond_wait_deadline(&ro_cond, deadline) != 0) {
+                        if (fiber_is_cancelled()) diag_set(FiberIsCancelled);
 			return -1;
 		}
 	}
diff --git a/src/lib/core/fiber_cond.c b/src/lib/core/fiber_cond.c
index 904a350d9..b0645069e 100644
--- a/src/lib/core/fiber_cond.c
+++ b/src/lib/core/fiber_cond.c
@@ -108,6 +108,7 @@ fiber_cond_wait_timeout(struct fiber_cond *c, double timeout)
 		diag_set(TimedOut);
 		return -1;
 	}
+	if (fiber_is_cancelled()) return -1;
 	return 0;
 }
 
diff --git a/test/app-tap/gh-5013-fiber-cancel.test.lua b/test/app-tap/gh-5013-fiber-cancel.test.lua
new file mode 100755
index 000000000..ae805c5bf
--- /dev/null
+++ b/test/app-tap/gh-5013-fiber-cancel.test.lua
@@ -0,0 +1,23 @@
+#!/usr/bin/env tarantool
+
+local tap = require('tap')
+local fiber = require('fiber')
+local test = tap.test("gh-5013-fiber-cancel")
+
+test:plan(2)
+
+local result = {}
+
+function test_f()
+    local cond = fiber.cond() 
+    local res, err = pcall(cond.wait, cond) 
+    result.res = res
+    result.err = err
+end
+
+local f = fiber.create(test_f)
+f:cancel()
+fiber.yield()
+
+test:ok(result.res == false, tostring(result.res))
+test:ok(tostring(result.err) == 'fiber is cancelled', tostring(result.err))
diff --git a/test/box/net.box_fiber_cancel_gh-4834.result b/test/box/net.box_fiber_cancel_gh-4834.result
new file mode 100644
index 000000000..eab0a5e4d
--- /dev/null
+++ b/test/box/net.box_fiber_cancel_gh-4834.result
@@ -0,0 +1,65 @@
+-- test-run result file version 2
+remote = require 'net.box'
+ | ---
+ | ...
+fiber = require 'fiber'
+ | ---
+ | ...
+test_run = require('test_run').new()
+ | ---
+ | ...
+
+-- #4834: Cancelling fiber doesn't interrupt netbox operations
+function infinite_call() fiber.channel(1):get() end
+ | ---
+ | ...
+box.schema.func.create('infinite_call')
+ | ---
+ | ...
+box.schema.user.grant('guest', 'execute', 'function', 'infinite_call')
+ | ---
+ | ...
+
+error_msg = nil
+ | ---
+ | ...
+test_run:cmd("setopt delimiter ';'")
+ | ---
+ | - true
+ | ...
+function gh4834()
+    local cn = remote.connect(box.cfg.listen)
+    local f = fiber.new(function()
+        _, error_msg = pcall(cn.call, cn, 'infinite_call')
+    end)
+    f:set_joinable(true)
+    fiber.yield()
+    f:cancel()
+    f:join()
+    cn:close()
+end;
+ | ---
+ | ...
+test_run:cmd("setopt delimiter ''");
+ | ---
+ | - true
+ | ...
+gh4834()
+ | ---
+ | ...
+error_msg
+ | ---
+ | - fiber is cancelled
+ | ...
+box.schema.func.drop('infinite_call')
+ | ---
+ | ...
+infinite_call = nil
+ | ---
+ | ...
+channel = nil
+ | ---
+ | ...
+error_msg = nil
+ | ---
+ | ...
diff --git a/test/box/net.box_fiber_cancel_gh-4834.test.lua b/test/box/net.box_fiber_cancel_gh-4834.test.lua
new file mode 100644
index 000000000..06fb3ceac
--- /dev/null
+++ b/test/box/net.box_fiber_cancel_gh-4834.test.lua
@@ -0,0 +1,29 @@
+remote = require 'net.box'
+fiber = require 'fiber'
+test_run = require('test_run').new()
+
+-- #4834: Cancelling fiber doesn't interrupt netbox operations
+function infinite_call() fiber.channel(1):get() end
+box.schema.func.create('infinite_call')
+box.schema.user.grant('guest', 'execute', 'function', 'infinite_call')
+
+error_msg = nil
+test_run:cmd("setopt delimiter ';'")
+function gh4834()
+    local cn = remote.connect(box.cfg.listen)
+    local f = fiber.new(function()
+        _, error_msg = pcall(cn.call, cn, 'infinite_call')
+    end)
+    f:set_joinable(true)
+    fiber.yield()
+    f:cancel()
+    f:join()
+    cn:close()
+end;
+test_run:cmd("setopt delimiter ''");
+gh4834()
+error_msg
+box.schema.func.drop('infinite_call')
+infinite_call = nil
+channel = nil
+error_msg = nil
-- 
2.17.1