zig

commit 0b2ee093788ba84c5d130c021f347844b5939889 (tree)
parent c9e02d3e69f909a6eb215286c6109f2b3f1e68a2
Author: r00ster91 <r00ster91@proton.me>
Date:   Tue, 21 Feb 2023 18:09:00 +0100

std.Thread.setName: use unused code

I noticed a comment saying that the intent of a code's author was unclear.
What happened is that the author forgot to put the check for whether the
thread is the calling thread (`self.getHandle() ==
std.c.pthread_self()`) in the `if (use_pthreads)`.
If the thread is the calling thread, we use `prctl` to set or get the
thread's name and it does not take a thread id because it knows the id
of the thread we're calling `getName` or `setName` from.
I have found a source saying that using `pthread_setname_np` on either the calling thread
or any other thread by thread id would work too (so we don't need to
call `prctl`) but I was not sure if that is the case on all systems
so we keep using `pthread_setname_np` if we have a
specific thread that is not the thread we're calling from, and `prctl`
otherwise.

Diffstat:
M
lib/std/Thread.zig
 | 
31
+++++++++++++++++--------------

1 file changed, 17 insertions(+), 14 deletions(-)
diff --git a/lib/std/Thread.zig b/lib/std/Thread.zig
@@ -62,18 +62,20 @@ pub fn setName(self: Thread, name: []const u8) SetNameError!void {
 
     switch (target.os.tag) {
         .linux => if (use_pthreads) {
-            const err = std.c.pthread_setname_np(self.getHandle(), name_with_terminator.ptr);
-            switch (err) {
-                .SUCCESS => return,
-                .RANGE => unreachable,
-                else => |e| return os.unexpectedErrno(e),
-            }
-        } else if (use_pthreads and self.getHandle() == std.c.pthread_self()) {
-            // TODO: this is dead code. what did the author of this code intend to happen here?
-            const err = try os.prctl(.SET_NAME, .{@ptrToInt(name_with_terminator.ptr)});
-            switch (@intToEnum(os.E, err)) {
-                .SUCCESS => return,
-                else => |e| return os.unexpectedErrno(e),
+            if (self.getHandle() == std.c.pthread_self()) {
+                // Set the name of the calling thread (no thread id required).
+                const err = try os.prctl(.SET_NAME, .{@ptrToInt(name_with_terminator.ptr)});
+                switch (@intToEnum(os.E, err)) {
+                    .SUCCESS => return,
+                    else => |e| return os.unexpectedErrno(e),
+                }
+            } else {
+                const err = std.c.pthread_setname_np(self.getHandle(), name_with_terminator.ptr);
+                switch (err) {
+                    .SUCCESS => return,
+                    .RANGE => unreachable,
+                    else => |e| return os.unexpectedErrno(e),
+                }
             }
         } else {
             var buf: [32]u8 = undefined;
@@ -177,6 +179,7 @@ pub fn getName(self: Thread, buffer_ptr: *[max_name_len:0]u8) GetNameError!?[]co
                 else => |e| return os.unexpectedErrno(e),
             }
         } else if (use_pthreads and self.getHandle() == std.c.pthread_self()) {
+            // Get the name of the calling thread (no thread id required).
             const err = try os.prctl(.GET_NAME, .{@ptrToInt(buffer.ptr)});
             switch (@intToEnum(os.E, err)) {
                 .SUCCESS => return std.mem.sliceTo(buffer, 0),
@@ -325,10 +328,10 @@ pub const SpawnError = error{
     Unexpected,
 };
 
-/// Spawns a new thread which executes `function` using `args` and returns a handle the spawned thread.
+/// Spawns a new thread which executes `function` using `args` and returns a handle to the spawned thread.
 /// `config` can be used as hints to the platform for now to spawn and execute the `function`.
 /// The caller must eventually either call `join()` to wait for the thread to finish and free its resources
-/// or call `detach()` to excuse the caller from calling `join()` and have the thread clean up its resources on completion`.
+/// or call `detach()` to excuse the caller from calling `join()` and have the thread clean up its resources on completion.
 pub fn spawn(config: SpawnConfig, comptime function: anytype, args: anytype) SpawnError!Thread {
     if (builtin.single_threaded) {
         @compileError("Cannot spawn thread when building in single-threaded mode");