gfx-rs/wgpu · error

error writing `lock::observing::Action`

Error message

error writing `lock::observing::Action`

What it means

Panic in lock observation logging: write_all to the observation log file failed (disk full, closed file, or I/O error) after the action was serialized. The faulty input is the log file/its underlying storage.

Source

Thrown at wgpu-core/src/lock/observing.rs:424

    fn write_rank(&mut self, rank: LockRankSet) {
        self.write_action(&Action::Rank {
            bit: rank.number(),
            member_name: rank.member_name(),
            const_name: rank.const_name(),
        });
    }

    fn write_action(&mut self, action: &Action) {
        use std::io::Write;

        self.buffer.clear();
        ron::ser::to_writer(&mut self.buffer, &action)
            .expect("error serializing `lock::observing::Action`");
        self.buffer.push('\n');
        self.log_file
            .write_all(self.buffer.as_bytes())
            .expect("error writing `lock::observing::Action`");
    }
}

/// An action logged by a thread that is observing lock acquisition order.
///
/// Each thread's log file is a sequence of these enums, serialized
/// using the [`ron`] crate, one action per line.
///
/// Lock observation cannot assume that there will be any convenient
/// finalization point before the program exits, so in practice,
/// actions must be written immediately when they occur. This means we
/// can't, say, accumulate tables and write them out when they're
/// complete. The `lock-analyzer` binary is then responsible for
/// consolidating the data into a single table of observed transitions.
#[derive(serde::Serialize)]
enum Action {
    /// A location that we will refer to in later actions.
    ///

View on GitHub (pinned to 3e11ff59bf)

Solutions

1. Ensure the observation directory and disk have space and remain writable for the process lifetime
2. Disable lock observation if logging is not essential

When it happens

Trigger: Thrown at wgpu-core/src/lock/observing.rs:424 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of gfx-rs/wgpu@3e11ff59bf (2026-09-03). Data as JSON: /api/errors/89cd533e0b9a0350. Report an issue: GitHub.