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termio/exec: fix 100% CPU usage after wait-after-command process exits #4171

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Jan 8, 2025
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termio/exec: fix 100% CPU usage after wait-after-command process exits #4171

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25 changes: 16 additions & 9 deletions src/termio/Exec.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -179,8 +179,11 @@ pub fn threadExit(self: *Exec, td: *termio.Termio.ThreadData) void {
// Quit our read thread after exiting the subprocess so that
// we don't get stuck waiting for data to stop flowing if it is
// a particularly noisy process.
_ = posix.write(exec.read_thread_pipe, "x") catch |err|
log.warn("error writing to read thread quit pipe err={}", .{err});
if (exec.read_thread_pipe) |pipe| {
posix.close(pipe);
// Tell deinit that we've already closed the pipe
exec.read_thread_pipe = null;
}

if (comptime builtin.os.tag == .windows) {
// Interrupt the blocking read so the thread can see the quit message
Expand Down Expand Up @@ -639,7 +642,7 @@ pub const ThreadData = struct {

/// Reader thread state
read_thread: std.Thread,
read_thread_pipe: posix.fd_t,
read_thread_pipe: ?posix.fd_t,
read_thread_fd: posix.fd_t,

/// The timer to detect termios state changes.
Expand All @@ -652,7 +655,8 @@ pub const ThreadData = struct {
termios_mode: ptypkg.Mode = .{},

pub fn deinit(self: *ThreadData, alloc: Allocator) void {
posix.close(self.read_thread_pipe);
// If the pipe isn't closed, close it.
if (self.read_thread_pipe) |pipe| posix.close(pipe);

// Clear our write pools. We know we aren't ever going to do
// any more IO since we stop our data stream below so we can just
Expand Down Expand Up @@ -1433,9 +1437,12 @@ pub const ReadThread = struct {
};

// This happens on macOS instead of WouldBlock when the
// child process dies. To be safe, we just break the loop
// and let our poll happen.
if (n == 0) break;
// child process dies. It's equivalent to NotOpenForReading
// so we can just exit.
if (n == 0) {
log.info("io reader exiting", .{});
return;
}

// log.info("DATA: {d}", .{n});
@call(.always_inline, termio.Termio.processOutput, .{ io, buf[0..n] });
Expand All @@ -1447,8 +1454,8 @@ pub const ReadThread = struct {
return;
};

// If our quit fd is set, we're done.
if (pollfds[1].revents & posix.POLL.IN != 0) {
// If our quit fd is closed, we're done.
if (pollfds[1].revents & posix.POLL.HUP != 0) {
log.info("read thread got quit signal", .{});
return;
}
Expand Down