n-api: detect deadlocks in thread-safe function #32689

gabrielschulhof · 2020-04-06T17:45:45Z

We introduce status napi_would_deadlock to be used as a return status
by napi_call_threadsafe_function if the call is made with
napi_tsfn_blocking on the main thread and the queue is full.

Fixes: #32615
Signed-off-by: @gabrielschulhof

Checklist

make -j4 test (UNIX), or vcbuild test (Windows) passes
tests and/or benchmarks are included
documentation is changed or added
commit message follows commit guidelines

nodejs-github-bot · 2020-04-06T17:48:19Z

CI: https://ci.nodejs.org/job/node-test-pull-request/30503/

addaleax · 2020-04-06T17:51:12Z

src/node_api.cc

@@ -148,12 +149,15 @@ class ThreadSafeFunction : public node::AsyncResource {

  napi_status Push(void* data, napi_threadsafe_function_call_mode mode) {
    node::Mutex::ScopedLock lock(this->mutex);
+    uv_thread_t the_thread = uv_thread_self();


Suggested change

uv_thread_t the_thread = uv_thread_self();

uv_thread_t current_thread = uv_thread_self();

addaleax · 2020-04-06T17:53:33Z

doc/api/n-api.md

+main thread, it will return `napi_would_deadlock` if the queue is full and it
+was called with `napi_tsfn_blocking`. The reason for this is that the main
+thread is responsible for reducing the number of items in the queue so, if it
+waits for room to become available on the queue, then it will deadlock.


Add a changes: entry for napi_create_threadsafe_function below?

gabrielschulhof · 2020-04-06T18:37:20Z

@addaleax I updated the variable name, added the changes: to napi_call_threadsafe_function() and re-worder the documentation about its return value a bit.

nodejs-github-bot · 2020-04-06T19:57:28Z

CI: https://ci.nodejs.org/job/node-test-pull-request/30516/

nodejs-github-bot · 2020-04-06T20:55:23Z

CI: https://ci.nodejs.org/job/node-test-pull-request/30517/ ✔️

legendecas · 2020-04-07T02:10:04Z

doc/api/n-api.md

+changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/32689
+    description: Return `napi_would_deadlock` when called from the main thread.


Suggested change

description: Return `napi_would_deadlock` when called from the main thread.

description: Return `napi_would_deadlock` if called with `napi_tsfn_blocking` from the main thread and the queue is full.

Just another clarification...

mhdawson

LGTM

nodejs-github-bot · 2020-04-09T07:05:37Z

CI: https://ci.nodejs.org/job/node-test-pull-request/30574/

We introduce status `napi_would_deadlock` to be used as a return status by `napi_call_threadsafe_function` if the call is made with `napi_tsfn_blocking` on the main thread and the queue is full. PR-URL: nodejs#32689 Fixes: nodejs#32615 Signed-off-by: Gabriel Schulhof <[email protected]>

nodejs-github-bot · 2020-04-09T07:39:12Z

CI: https://ci.nodejs.org/job/node-test-pull-request/30575/

nodejs-github-bot · 2020-04-09T08:33:26Z

CI: https://ci.nodejs.org/job/node-test-pull-request/30577/ ✔️

gabrielschulhof · 2020-04-09T09:44:34Z

Landed in aeb7084.

We introduce status `napi_would_deadlock` to be used as a return status by `napi_call_threadsafe_function` if the call is made with `napi_tsfn_blocking` on the main thread and the queue is full. PR-URL: #32689 Fixes: #32615 Signed-off-by: Gabriel Schulhof <[email protected]> Reviewed-By: James M Snell <[email protected]> Reviewed-By: Anna Henningsen <[email protected]> Reviewed-By: Colin Ihrig <[email protected]> Reviewed-By: David Carlier <[email protected]> Reviewed-By: Chengzhong Wu <[email protected]> Reviewed-By: Michael Dawson <[email protected]>

Notable changes: New file system APIs: * Added a new function, `fs.readv` (with sync and promisified versions). This function takes an array of `ArrayBufferView` elements and will write the data it reads sequentially to the buffers (Sk Sajidul Kadir). #32356 * A new overload is available for `fs.readSync`, which allows to optionally pass any of the `offset`, `length` and `position` parameters. #32460 Other changes: * dns: * Added the `dns.ALL` flag, that can be passed to `dns.lookup()` with `dns.V4MAPPED` to return resolved IPv6 addresses as well as IPv4 mapped IPv6 addresses (murgatroid99). #32183 * http: * The default maximum HTTP header size was changed from 8KB to 16KB (rosaxny). #32520 * n-api: * Calls to `napi_call_threadsafe_function` from the main thread can now return the `napi_would_deadlock` status in certain circumstances (Gabriel Schulhof). #32689 * util: * Added a new `maxStrLength` option to `util.inspect`, to control the maximum length of printed strings. Its default value is `Infinity` (rosaxny). #32392 * worker: * Added support for passing a `transferList` along with `workerData` to the `Worker` constructor (Juan José Arboleda). #32278 New core collaborators: With this release, we welcome three new Node.js core collaborators: * himself65. #32734 * flarna (Gerhard Stoebich). #32620 * mildsunrise (Alba Mendez). #32525 PR-URL: #32813

himself65 · 2020-04-15T06:47:30Z

just tip. downstream #32689 or #32860

gabrielschulhof added semver-minor PRs that contain new features and should be released in the next minor version. node-api Issues and PRs related to the Node-API. labels Apr 6, 2020

gabrielschulhof requested review from addaleax, legendecas and mhdawson April 6, 2020 17:45

nodejs-github-bot added the c++ Issues and PRs that require attention from people who are familiar with C++. label Apr 6, 2020

gabrielschulhof force-pushed the tsfn-avoid-deadlock branch from 968f06d to f93f12e Compare April 6, 2020 17:47

gabrielschulhof force-pushed the tsfn-avoid-deadlock branch from f93f12e to 7b258a1 Compare April 6, 2020 17:47

addaleax approved these changes Apr 6, 2020

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jasnell approved these changes Apr 7, 2020

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legendecas approved these changes Apr 7, 2020

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devnexen approved these changes Apr 7, 2020

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cjihrig approved these changes Apr 7, 2020

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mhdawson approved these changes Apr 7, 2020

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gabrielschulhof force-pushed the tsfn-avoid-deadlock branch from 439af5e to 6322b5d Compare April 9, 2020 07:04

gabrielschulhof force-pushed the tsfn-avoid-deadlock branch from 6322b5d to 929cdb4 Compare April 9, 2020 07:09

gabrielschulhof force-pushed the tsfn-avoid-deadlock branch from 929cdb4 to 75b2509 Compare April 9, 2020 07:10

gabrielschulhof force-pushed the tsfn-avoid-deadlock branch from 75b2509 to e5c61e8 Compare April 9, 2020 07:13

gabrielschulhof closed this Apr 9, 2020

targos mentioned this pull request Apr 13, 2020

v13.13.0 release proposal #32813

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gabrielschulhof deleted the tsfn-avoid-deadlock branch April 13, 2020 18:34

gabrielschulhof mentioned this pull request Apr 15, 2020

n-api: detect deadlocks in thread-safe function (take two) #32860

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n-api: detect deadlocks in thread-safe function #32689

n-api: detect deadlocks in thread-safe function #32689

gabrielschulhof commented Apr 6, 2020 •

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himself65 commented Apr 15, 2020

	uv_thread_t the_thread = uv_thread_self();
	uv_thread_t current_thread = uv_thread_self();

	description: Return `napi_would_deadlock` when called from the main thread.
	description: Return `napi_would_deadlock` if called with `napi_tsfn_blocking` from the main thread and the queue is full.

n-api: detect deadlocks in thread-safe function #32689

n-api: detect deadlocks in thread-safe function #32689

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