src/librustc_data_structures/jobserver.rs

   1 pub use jobserver_crate::Client;
   2 use lazy_static::lazy_static;
   3
   4 lazy_static! {
   5     // We can only call `from_env` once per process
   6
   7     // Note that this is unsafe because it may misinterpret file descriptors
   8     // on Unix as jobserver file descriptors. We hopefully execute this near
   9     // the beginning of the process though to ensure we don't get false
  10     // positives, or in other words we try to execute this before we open
  11     // any file descriptors ourselves.
  12     //
  13     // Pick a "reasonable maximum" if we don't otherwise have
  14     // a jobserver in our environment, capping out at 32 so we
  15     // don't take everything down by hogging the process run queue.
  16     // The fixed number is used to have deterministic compilation
  17     // across machines.
  18     //
  19     // Also note that we stick this in a global because there could be
  20     // multiple rustc instances in this process, and the jobserver is
  21     // per-process.
  22     static ref GLOBAL_CLIENT: Client = unsafe {
  23         Client::from_env().unwrap_or_else(|| {
  24             let client = Client::new(32).expect("failed to create jobserver");
  25             // Acquire a token for the main thread which we can release later
  26             client.acquire_raw().ok();
  27             client
  28         })
  29     };
  30 }
  31
  32 pub fn client() -> Client {
  33     GLOBAL_CLIENT.clone()
  34 }
  35
  36 pub fn acquire_thread() {
  37     GLOBAL_CLIENT.acquire_raw().ok();
  38 }
  39
  40 pub fn release_thread() {
  41     GLOBAL_CLIENT.release_raw().ok();
  42 }