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ke/mutex: wrap lines

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Loïc Grégoire
2026-08-05 17:52:17 -04:00
parent bec872bc26
commit 13375f294c
1 changed files with 42 additions and 9 deletions
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src/kern/mutex.zig
+42 -9
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@@ -21,8 +21,14 @@ pub const Mutex = struct {
const ipl = ke.ipl.raise(.Dispatch);
const curtd = ki.sched.percpu.local().current_thread.?;
// Very fast path: the lock is uncontended and we can acquire it immediately.
const cur_owner = m.owner.cmpxchgStrong(null, curtd, .acquire, .monotonic);
// Very fast path: the lock is uncontended and we can acquire it
//immediately.
const cur_owner = m.owner.cmpxchgStrong(
null,
curtd,
.acquire,
.monotonic,
);
if (cur_owner == null) {
ke.ipl.lower(ipl);
@@ -36,7 +42,12 @@ pub const Mutex = struct {
continue;
}
if (m.owner.cmpxchgWeak(null, curtd, .acquire, .monotonic) != null) {
if (m.owner.cmpxchgWeak(
null,
curtd,
.acquire,
.monotonic,
) != null) {
continue;
}
@@ -52,17 +63,32 @@ pub const Mutex = struct {
if (owner == null) {
// Lock was released between lookup and here.
ki.turnstile.exit(m);
if (m.owner.cmpxchgStrong(null, curtd, .acquire, .monotonic) == null) {
if (m.owner.cmpxchgStrong(
null,
curtd,
.acquire,
.monotonic,
) == null) {
break;
}
continue;
}
// Block until woken.
ki.turnstile.block(ts, m, .{ .single = owner.? }, .Exclusive);
ki.turnstile.block(
ts,
m,
.{ .single = owner.? },
.Exclusive,
);
// Re-try acquisition after wakeup.
if (m.owner.cmpxchgStrong(null, curtd, .acquire, .monotonic) == null) {
if (m.owner.cmpxchgStrong(
null,
curtd,
.acquire,
.monotonic,
) == null) {
break;
}
}
@@ -83,10 +109,17 @@ pub const Mutex = struct {
return;
}
// Note: wake up all waiters. This so-called "lock barging" (name from WTF::ParkingLot)
// has been shown to be better because this avoids lock convoys, see this mysterious 70s paper:
// Note: wake up all waiters.
// This so-called "lock barging" (name from WTF::ParkingLot) has been
// to be better because this avoids lock convoys,
// see this mysterious 70s paper:
// https://dl.acm.org/doi/pdf/10.1145/850657.850659
ki.turnstile.wakeup(ts.?, .Exclusive, ts.?.waiters, null);
ki.turnstile.wakeup(
ts.?,
.Exclusive,
ts.?.waiters,
null,
);
ki.turnstile.exit(m);
ke.ipl.lower(ipl);