Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
unwind: Make unwind_task_info::unwind_mask consistent
The unwind_task_info::unwind_mask was manipulated using a mixture of:
regular store
WRITE_ONCE()
try_cmpxchg()
set_bit()
atomic_long_*()
Clean up and make it consistently atomic_long_t.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20250924080119.384384486@infradead.org
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-11
+2
-2
include/linux/unwind_deferred.h
+2
-2
include/linux/unwind_deferred.h
···
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static __always_inline void unwind_reset_info(void)
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{
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struct unwind_task_info *info = ¤t->unwind_info;
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unsigned long bits = info->unwind_mask;
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+
unsigned long bits = atomic_long_read(&info->unwind_mask);
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/* Was there any unwinding? */
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if (likely(!bits))
···
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/* Is a task_work going to run again before going back */
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if (bits & UNWIND_PENDING)
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return;
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-
} while (!try_cmpxchg(&info->unwind_mask, &bits, 0UL));
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} while (!atomic_long_try_cmpxchg(&info->unwind_mask, &bits, 0UL));
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current->unwind_info.id.id = 0;
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if (unlikely(info->cache)) {
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-1
include/linux/unwind_deferred_types.h
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-1
include/linux/unwind_deferred_types.h
···
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#define _LINUX_UNWIND_USER_DEFERRED_TYPES_H
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#include <linux/types.h>
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#include <linux/atomic.h>
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struct unwind_cache {
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unsigned long unwind_completed;
···
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};
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struct unwind_task_info {
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unsigned long unwind_mask;
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+
atomic_long_t unwind_mask;
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struct unwind_cache *cache;
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struct callback_head work;
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union unwind_task_id id;
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-8
kernel/unwind/deferred.c
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-8
kernel/unwind/deferred.c
···
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static inline bool unwind_pending(struct unwind_task_info *info)
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{
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-
return test_bit(UNWIND_PENDING_BIT, &info->unwind_mask);
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+
return atomic_long_read(&info->unwind_mask) & UNWIND_PENDING;
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}
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/*
···
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cache->nr_entries = trace->nr;
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/* Clear nr_entries on way back to user space */
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set_bit(UNWIND_USED_BIT, &info->unwind_mask);
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atomic_long_or(UNWIND_USED, &info->unwind_mask);
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return 0;
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}
···
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/* Clear pending bit but make sure to have the current bits */
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bits = atomic_long_fetch_andnot(UNWIND_PENDING,
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(atomic_long_t *)&info->unwind_mask);
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&info->unwind_mask);
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/*
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* From here on out, the callback must always be called, even if it's
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* just an empty trace.
···
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*cookie = get_cookie(info);
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old = READ_ONCE(info->unwind_mask);
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old = atomic_long_read(&info->unwind_mask);
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/* Is this already queued or executed */
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if (old & bit)
···
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* to have a callback.
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*/
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bits = UNWIND_PENDING | bit;
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old = atomic_long_fetch_or(bits, (atomic_long_t *)&info->unwind_mask);
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old = atomic_long_fetch_or(bits, &info->unwind_mask);
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if (old & bits) {
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/*
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* If the work's bit was set, whatever set it had better
···
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ret = task_work_add(current, &info->work, twa_mode);
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if (WARN_ON_ONCE(ret))
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WRITE_ONCE(info->unwind_mask, 0);
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atomic_long_set(&info->unwind_mask, 0);
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return ret;
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}
···
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guard(rcu)();
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/* Clear this bit from all threads */
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for_each_process_thread(g, t) {
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clear_bit(bit, &t->unwind_info.unwind_mask);
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atomic_long_andnot(BIT(bit),
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&t->unwind_info.unwind_mask);
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if (t->unwind_info.cache)
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clear_bit(bit, &t->unwind_info.cache->unwind_completed);
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}
···
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memset(info, 0, sizeof(*info));
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init_task_work(&info->work, unwind_deferred_task_work);
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info->unwind_mask = 0;
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atomic_long_set(&info->unwind_mask, 0);
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}
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void unwind_task_free(struct task_struct *task)