Re: [PATCH v10 08/14] unwind deferred: Use bitmask to determine which callbacks to call
From: Peter Zijlstra <peterz@infradead.org>
Date: 2025-06-20 08:16:00
Also in:
bpf, lkml
On Tue, Jun 10, 2025 at 08:54:29PM -0400, Steven Rostedt wrote:
void unwind_deferred_cancel(struct unwind_work *work)
{
+ struct task_struct *g, *t;
+
if (!work)
return;
guard(mutex)(&callback_mutex);
list_del(&work->list);
+
+ clear_bit(work->bit, &unwind_mask);atomic bitop
quoted hunk ↗ jump to hunk
+ + guard(rcu)(); + /* Clear this bit from all threads */ + for_each_process_thread(g, t) { + clear_bit(work->bit, &t->unwind_info.unwind_mask); + } } int unwind_deferred_init(struct unwind_work *work, unwind_callback_t func)@@ -256,6 +278,14 @@ int unwind_deferred_init(struct unwind_work *work, unwind_callback_t func) memset(work, 0, sizeof(*work)); guard(mutex)(&callback_mutex); + + /* See if there's a bit in the mask available */ + if (unwind_mask == ~0UL) + return -EBUSY; + + work->bit = ffz(unwind_mask); + unwind_mask |= BIT(work->bit);
regular or
quoted hunk ↗ jump to hunk
+ list_add(&work->list, &callbacks); work->func = func; return 0;@@ -267,6 +297,7 @@ void unwind_task_init(struct task_struct *task) memset(info, 0, sizeof(*info)); init_task_work(&info->work, unwind_deferred_task_work); + info->unwind_mask = 0; }
Which is somewhat inconsistent; __clear_bit()/__set_bit() or: unwind_mask &= ~BIT() / unwind_mask |= BIT()