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Auto merge of #6748 - alexcrichton:release-then-acquire, r=ehuss
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Release a jobserver token while locking a file

This is a possible solution to #6747, but we'll ideally get some testing
in before landing!
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bors committed Mar 15, 2019
2 parents 2ed31b0 + 512fccb commit efd29db
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Showing 3 changed files with 23 additions and 12 deletions.
2 changes: 1 addition & 1 deletion Cargo.toml
Original file line number Diff line number Diff line change
Expand Up @@ -39,7 +39,7 @@ hex = "0.3"
home = "0.3"
ignore = "0.4"
lazy_static = "1.2.0"
jobserver = "0.1.11"
jobserver = "0.1.13"
lazycell = "1.2.0"
libc = "0.2"
log = "0.4.6"
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10 changes: 1 addition & 9 deletions appveyor.yml
Original file line number Diff line number Diff line change
Expand Up @@ -2,16 +2,12 @@ environment:
matrix:
- TARGET: x86_64-pc-windows-msvc
OTHER_TARGET: i686-pc-windows-msvc
- TARGET: x86_64-pc-windows-msvc
MINIMAL_VERSIONS: true
CFG_DISABLE_CROSS_TESTS: 1

install:
- if NOT defined APPVEYOR_PULL_REQUEST_NUMBER if "%APPVEYOR_REPO_BRANCH%" == "master" appveyor exit
- appveyor-retry appveyor DownloadFile https://win.rustup.rs/ -FileName rustup-init.exe
- rustup-init.exe -y --default-host x86_64-pc-windows-msvc --default-toolchain nightly
- set PATH=%PATH%;C:\Users\appveyor\.cargo\bin
- if defined MINIMAL_VERSIONS rustup toolchain install 1.31.0
- if defined OTHER_TARGET rustup target add %OTHER_TARGET%
- rustc -V
- cargo -V
Expand All @@ -22,8 +18,4 @@ clone_depth: 1
build: false

test_script:
# we don't have ci time to run the full `cargo test` with `minimal-versions` like
# - if defined MINIMAL_VERSIONS cargo +nightly generate-lockfile -Z minimal-versions && cargo +stable test
# so we just run `cargo check --tests` like
- if defined MINIMAL_VERSIONS cargo +nightly generate-lockfile -Z minimal-versions && cargo +1.31.0 check --tests --features=deny-warnings
- if NOT defined MINIMAL_VERSIONS cargo test --features=deny-warnings
- cargo test --features=deny-warnings
23 changes: 21 additions & 2 deletions src/cargo/util/flock.rs
Original file line number Diff line number Diff line change
Expand Up @@ -312,8 +312,27 @@ fn acquire(
let msg = format!("waiting for file lock on {}", msg);
config.shell().status_with_color("Blocking", &msg, Cyan)?;

block().chain_err(|| format!("failed to lock file: {}", path.display()))?;
return Ok(());
// We're about to block the current process and not really do anything
// productive for what could possibly be a very long time. We could be
// waiting, for example, on another Cargo to finish a download, finish an
// entire build, etc. Since we're not doing anything productive we're not
// making good use of our jobserver token, if we have one.
//
// This can typically come about if `cargo` is invoked from `make` (or some
// other jobserver-providing system). In this situation it's actually best
// if we release the token back to the original jobserver to let some other
// cpu-hungry work continue to make progress. After we're done blocking
// we'll block waiting to reacquire a token as we'll probably be doing cpu
// hungry work ourselves.
let jobserver = config.jobserver_from_env();
if let Some(server) = jobserver {
server.release_raw()?;
}
let result = block().chain_err(|| format!("failed to lock file: {}", path.display()));
if let Some(server) = jobserver {
server.acquire_raw()?;
}
return Ok(result?);

#[cfg(all(target_os = "linux", not(target_env = "musl")))]
fn is_on_nfs_mount(path: &Path) -> bool {
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