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Watch.zig: fixes for windows implementation

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Using --watch I noticed a couple of issues with my initial attempt. 1) The index I used as 'completion key' was not stable over time, when directories are being added/removed the key no longer corresponds with the intended dir. 2) There exists a race condition in which we receive a completion notification for a directory that was removed. My solution is to generate a key value and associate it with each Directory.
This commit is contained in:
Jarrod Meyer 2024-08-01 22:28:06 -04:00 committed by Andrew Kelley
parent 78fb9c0a17
commit 9be10ea964
1 changed files with 20 additions and 9 deletions
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29
lib/std/Build/Watch.zig
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@ -242,8 +242,9 @@ const Os = switch (builtin.os.tag) {
/// Keyed differently but indexes correspond 1:1 with `dir_table`.
handle_table: HandleTable,
dir_list: std.ArrayListUnmanaged(*Directory),
dir_list: std.AutoArrayHashMapUnmanaged(usize, *Directory),
io_cp: ?windows.HANDLE,
counter: usize = 0,
const HandleTable = std.AutoArrayHashMapUnmanaged(FileId, ReactionSet);
@ -260,7 +261,8 @@ const Os = switch (builtin.os.tag) {
// https://learn.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-readdirectorychangesw#remarks
buffer: [64 * 1024]u8 align(@alignOf(windows.FILE_NOTIFY_INFORMATION)) = undefined,
fn readChanges(self: *@This()) !void {
/// Start listening for events, buffer field will be overwritten eventually.
fn startListening(self: *@This()) !void {
const r = windows.kernel32.ReadDirectoryChangesW(
self.handle,
@ptrCast(&self.buffer),
@ -394,6 +396,7 @@ const Os = switch (builtin.os.tag) {
if (bytes_returned == 0) {
std.log.warn("file system watch queue overflowed; falling back to fstat", .{});
markAllFilesDirty(w, gpa);
try dir.startListening();
return true;
}
var file_name_buf: [std.fs.max_path_bytes]u8 = undefined;
@ -418,7 +421,8 @@ const Os = switch (builtin.os.tag) {
offset += notify.NextEntryOffset;
}
try dir.readChanges();
// We call this now since at this point we have finished reading dir.buffer.
try dir.startListening();
return any_dirty;
}
@ -444,12 +448,14 @@ const Os = switch (builtin.os.tag) {
} else {
assert(dh_gop.index == gop.index);
dh_gop.value_ptr.* = .{};
try dir.readChanges();
try w.os.dir_list.insert(gpa, dh_gop.index, dir);
try dir.startListening();
const key = w.os.counter;
w.os.counter +%= 1;
try w.os.dir_list.put(gpa, key, dir);
w.os.io_cp = try windows.CreateIoCompletionPort(
dir.handle,
w.os.io_cp,
dh_gop.index,
key,
0,
);
}
@ -495,8 +501,8 @@ const Os = switch (builtin.os.tag) {
}
}
w.os.dir_list.items[i].deinit(gpa);
_ = w.os.dir_list.swapRemove(i);
w.os.dir_list.values()[i].deinit(gpa);
w.os.dir_list.swapRemoveAt(i);
w.dir_table.swapRemoveAt(i);
w.os.handle_table.swapRemoveAt(i);
}
@ -653,7 +659,12 @@ pub fn wait(w: *Watch, gpa: Allocator, timeout: Timeout) !WaitResult {
.Normal => {
if (bytes_transferred == 0)
break error.Unexpected;
break if (try Os.markDirtySteps(w, gpa, w.os.dir_list.items[key]))
// This 'orelse' detects a race condition that happens when we receive a
// completion notification for a directory that no longer exists in our list.
const dir = w.os.dir_list.get(key) orelse break .clean;
break if (try Os.markDirtySteps(w, gpa, dir))
.dirty
else
.clean;