jimzah/zig
1
0
Fork 0
mirror of https://github.com/ziglang/zig.git synced 2024-11-26 15:12:31 +00:00
Code Issues Actions 1 Packages Projects Releases Wiki Activity

std.Progress: fix data race

Browse Source 
In end(), the freelist pointer is owned so the bare store would be ok.
However, there is a load in start() that can happen at the same time, if
another start() and end() pair grabs that same index.

I don't think this fixes #21663 actually because even if the data race
corrupts the value for `next`, the cmpxchg protects the value from being
stored there.
This commit is contained in:
Andrew Kelley 2024-10-23 13:47:44 -07:00
parent 6bf52b0505
commit d210f733f8
1 changed files with 3 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
lib/std/Progress.zig
View File

@ -188,7 +188,8 @@ pub const Node = struct {
var opt_free_index = @atomicLoad(Node.OptionalIndex, freelist_head, .seq_cst);
while (opt_free_index.unwrap()) |free_index| {
const freelist_ptr = freelistByIndex(free_index);
opt_free_index = @cmpxchgWeak(Node.OptionalIndex, freelist_head, opt_free_index, freelist_ptr.*, .seq_cst, .seq_cst) orelse {
const next = @atomicLoad(Node.OptionalIndex, freelist_ptr, .seq_cst);
opt_free_index = @cmpxchgWeak(Node.OptionalIndex, freelist_head, opt_free_index, next, .seq_cst, .seq_cst) orelse {
// We won the allocation race.
return init(free_index, parent, name, estimated_total_items);
};
@ -249,7 +250,7 @@ pub const Node = struct {
const freelist_head = &global_progress.node_freelist_first;
var first = @atomicLoad(Node.OptionalIndex, freelist_head, .seq_cst);
while (true) {
freelistByIndex(index).* = first;
@atomicStore(Node.OptionalIndex, freelistByIndex(index), first, .seq_cst);
first = @cmpxchgWeak(Node.OptionalIndex, freelist_head, first, index.toOptional(), .seq_cst, .seq_cst) orelse break;
}
} else {