commit 2da3ed216a288efe48979a96acbafede45866ebd
parent 80e901354972f70791d7e889d347c2ab7a164ded
Author: Drew DeVault <sir@cmpwn.com>
Date: Sun, 27 Jun 2021 10:54:54 -0400
hare::module: use lock-free atomic manifest writes
This fixes a race condition in parallel builds by writing the manifest
to a temporary path and then moving it into its final position.
Signed-off-by: Drew DeVault <sir@cmpwn.com>
Diffstat:
2 files changed, 14 insertions(+), 51 deletions(-)
diff --git a/hare/module/manifest.ha b/hare/module/manifest.ha
@@ -13,6 +13,7 @@ use path;
use strconv;
use strings;
use time;
+use temp;
// The manifest file format is a series of line-oriented records. Lines starting
// with # are ignored.
@@ -51,11 +52,6 @@ export fn manifest_load(ctx: *context, ident: ast::ident) (manifest | error) = {
let mpath = path::join(cachedir, "manifest");
defer free(mpath);
- // TODO: We can probably eliminate these locks by using atomic writes
- // instead
- let l = lock(ctx.fs, cachedir)?;
- defer unlock(ctx.fs, cachedir, l);
-
let file = match (fs::open(ctx.fs, mpath, fs::flags::RDONLY)) {
errors::noentry => return manifest,
err: fs::error => return err,
@@ -237,11 +233,11 @@ export fn manifest_write(ctx: *context, manifest: *manifest) (void | error) = {
let mpath = path::join(cachedir, "manifest");
defer free(mpath);
- let l = lock(ctx.fs, cachedir)?;
- defer unlock(ctx.fs, cachedir, l);
-
- let fd = fs::create(ctx.fs, mpath, 0o644)?;
- defer io::close(fd);
+ let fd = temp::named(ctx.fs, cachedir, io::mode::WRITE, 0o644)?;
+ defer {
+ fs::remove(ctx.fs, fd.name): void;
+ io::close(fd);
+ };
let ident = unparse::identstr(manifest.ident);
defer free(ident);
@@ -277,43 +273,8 @@ export fn manifest_write(ctx: *context, manifest: *manifest) (void | error) = {
fmt::fprintln(fd)?;
};
-};
-
-fn lock(fs: *fs::fs, cachedir: str) (*io::stream | error) = {
- // XXX: I wonder if this should be some generic function in fs or
- // something
- match (os::mkdirs(cachedir)) {
- errors::exists => void,
- void => void,
- e: fs::error => return e,
- };
- let lockpath = path::join(cachedir, "manifest.lock");
- defer free(lockpath);
-
- let logged = false;
- for (true) {
- match (fs::create(fs, lockpath, 0o644, fs::flags::EXCL)) {
- fd: *io::stream => return fd,
- (errors::busy | errors::exists) => void,
- err: fs::error => return err,
- };
- if (!logged) {
- fmt::errorfln("Waiting for lock on {}...", lockpath): void;
- logged = true;
- };
- time::sleep(1 * time::SECOND);
- };
- abort("Unreachable");
-};
-
-fn unlock(fs: *fs::fs, cachedir: str, s: *io::stream) void = {
- let lockpath = path::join(cachedir, "manifest.lock");
- defer free(lockpath);
- match (fs::remove(fs, lockpath)) {
- void => void,
- err: fs::error => abort("Error removing module lock"),
- };
+ fs::move(ctx.fs, fd.name, mpath)?;
};
fn input_finish(in: *input) void = {
diff --git a/temp/+linux.ha b/temp/+linux.ha
@@ -35,20 +35,22 @@ export fn file(
return match (os::create(get_tmpdir(), fmode, oflags)) {
// TODO: Add a custom "close" function which removes the named
// file
- err: fs::error => named(get_tmpdir(), iomode, mode...),
+ err: fs::error => named(os::cwd, get_tmpdir(), iomode, mode...),
s: *io::stream => s,
};
};
-// Creates a named temporary file in the given directory. The path to the
-// temporary file may be found via the name field of [[io::stream]]. The caller
-// is responsible for removing the file when they're done with it.
+// Creates a named temporary file in the given directory of the given
+// filesystem. The path to the temporary file may be found via the name field of
+// [[io::stream]]. The caller is responsible for removing the file when they're
+// done with it.
//
// The I/O mode must be either [[io::mode::WRITE]] or [[io::mode::RDWR]].
//
// Only one variadic argument may be provided, if at all, to specify the mode of
// the new file. The default is 0o644.
export fn named(
+ fs: *fs::fs,
path: str,
iomode: io::mode,
mode: fs::mode...
@@ -71,7 +73,7 @@ export fn named(
random::buffer(rand);
const id = *(&rand[0]: *u64);
const fpath = fmt::bsprintf(pathbuf, "{}/temp.{}", path, id);
- match (os::create(fpath, fmode, oflags)) {
+ match (fs::create(fs, fpath, fmode, oflags)) {
errors::exists => continue,
err: fs::error => return err,
s: *io::stream => return s,
