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fix: more fixing of fixes

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This commit is contained in:
CJ van den Berg 2026-03-15 00:27:52 +01:00
parent 190290e96c
commit 4339c122eb
Signed by: neurocyte
GPG key ID: 8EB1E1BB660E3FB9
3 changed files with 30 additions and 11 deletions
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21
src/backend/KQueue.zig
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@ -209,8 +209,8 @@ fn scan_dir(self: *@This(), allocator: std.mem.Allocator, dir_path: []const u8)
}
// Diff against snapshot under the lock; collect events to emit after releasing it.
// to_create / to_delete hold borrowed pointers into the snapshot (which uses
// allocator, not tmp); only the list metadata itself uses tmp.
// to_create / to_delete / new_dirs all use tmp (arena) so they are independent
// of the snapshot and remain valid after the mutex is released.
var to_create: std.ArrayListUnmanaged([]const u8) = .empty;
var to_delete: std.ArrayListUnmanaged([]const u8) = .empty;
var new_dirs: std.ArrayListUnmanaged([]const u8) = .empty;
@ -220,8 +220,12 @@ fn scan_dir(self: *@This(), allocator: std.mem.Allocator, dir_path: []const u8)
var to_delete_owned = false;
defer if (to_delete_owned) for (to_delete.items) |name| allocator.free(name);
// Use a boolean flag rather than errdefer to unlock the mutex. An errdefer
// scoped to the whole function would fire again after the explicit unlock below,
// double-unlocking the mutex (UB) if handler.change() later returns an error.
self.snapshots_mutex.lock();
errdefer self.snapshots_mutex.unlock();
var snapshots_locked = true;
defer if (snapshots_locked) self.snapshots_mutex.unlock();
{
for (current_dirs.items) |name| {
var path_buf: [std.fs.max_path_bytes]u8 = undefined;
@ -254,7 +258,10 @@ fn scan_dir(self: *@This(), allocator: std.mem.Allocator, dir_path: []const u8)
allocator.free(owned);
return e;
};
try to_create.append(tmp, owned);
// Dupe into tmp so to_create holds arena-owned strings that remain
// valid after the mutex is released, even if remove_watch() frees
// the snapshot entry concurrently.
try to_create.append(tmp, try tmp.dupe(u8, owned));
}
var sit = snapshot.iterator();
@ -265,6 +272,7 @@ fn scan_dir(self: *@This(), allocator: std.mem.Allocator, dir_path: []const u8)
for (to_delete.items) |name| _ = snapshot.fetchRemove(name);
to_delete_owned = true; // ownership transferred; defer will free all items
}
snapshots_locked = false;
self.snapshots_mutex.unlock();
// Emit all events outside the lock so handlers may safely call watch()/unwatch().
@ -449,7 +457,10 @@ fn take_snapshot(self: *@This(), allocator: std.mem.Allocator, dir_path: []const
for (names.items) |name| {
if (snapshot.contains(name)) continue;
const owned = try allocator.dupe(u8, name);
try snapshot.put(allocator, owned, {});
snapshot.put(allocator, owned, {}) catch |e| {
allocator.free(owned);
return e;
};
}
self.snapshots_mutex.unlock();
// Register a kqueue watch for each existing file so writes are detected.