Re: [PATCH v13 10/14] unwind: Clear unwind_mask on exit back to user space
From: Steven Rostedt <rostedt@goodmis.org>
Date: 2025-07-15 22:01:19
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bpf, lkml
On Tue, 15 Jul 2025 12:29:12 +0200 Peter Zijlstra [off-list ref] wrote:
The below is the last four patches rolled into one. Not been near a compiler.
And it shows ;-)
quoted hunk ↗ jump to hunk
@@ -117,13 +138,13 @@ static void unwind_deferred_task_work(st struct unwind_task_info *info = container_of(head, struct unwind_task_info, work); struct unwind_stacktrace trace; struct unwind_work *work; + unsigned long bits; u64 cookie; - if (WARN_ON_ONCE(!info->pending)) + if (WARN_ON_ONCE(!unwind_pending(info))) return; - /* Allow work to come in again */ - WRITE_ONCE(info->pending, 0); + bits = atomic_long_fetch_andnot(UNWIND_PENDING, &info->unwind_mask);
I may need to do what other parts of the kernel has done and turn the above into: bits = atomic_long_fetch_andnot(UNWIND_PENDING, (atomic_long_t *)&info->unwind_mask); As there's other bit manipulations that atomic_long does not take care of and it's making the code more confusing. When I looked to see how other users of atomic_long_andnot() did things, most just typecasted the value to use that function :-/ -- Steve
quoted hunk ↗ jump to hunk
/* * From here on out, the callback must always be called, even if it's@@ -136,9 +157,11 @@ static void unwind_deferred_task_work(st cookie = info->id.id; - guard(mutex)(&callback_mutex); - list_for_each_entry(work, &callbacks, list) { - work->func(work, &trace, cookie); + guard(srcu_lite)(&unwind_srcu); + list_for_each_entry_srcu(work, &callbacks, list, + srcu_read_lock_held(&unwind_srcu)) { + if (test_bit(work->bit, &bits)) + work->func(work, &trace, cookie); } }@@ -162,7 +185,7 @@ static void unwind_deferred_task_work(st * because it has already been previously called for the same entry context, * it will be called again with the same stack trace and cookie. * - * Return: 1 if the the callback was already queued. + * Return: 1 if the callback was already queued. * 0 if the callback successfully was queued. * Negative if there's an error. * @cookie holds the cookie of the first request by any user