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unwind: Make unwind_task_info::unwind_mask consistent

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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
This commit is contained in:
Peter Zijlstra
2025-09-22 16:09:17 +02:00
parent 42b9138f81
commit 639214f65b
3 changed files with 13 additions and 11 deletions
Download Patch File Download Diff File Expand all files Collapse all files

4
include/linux/unwind_deferred.h
View File

@@ -46,7 +46,7 @@ void unwind_deferred_task_exit(struct task_struct *task);
static __always_inline void unwind_reset_info(void)
{
struct unwind_task_info *info = &current->unwind_info;
unsigned long bits = info->unwind_mask;
unsigned long bits = atomic_long_read(&info->unwind_mask);
/* Was there any unwinding? */
if (likely(!bits))
@@ -56,7 +56,7 @@ static __always_inline void unwind_reset_info(void)
/* Is a task_work going to run again before going back */
if (bits & UNWIND_PENDING)
return;
} while (!try_cmpxchg(&info->unwind_mask, &bits, 0UL));
} while (!atomic_long_try_cmpxchg(&info->unwind_mask, &bits, 0UL));
current->unwind_info.id.id = 0;
if (unlikely(info->cache)) {

3
include/linux/unwind_deferred_types.h
View File

@@ -3,6 +3,7 @@
#define _LINUX_UNWIND_USER_DEFERRED_TYPES_H
#include <linux/types.h>
#include <linux/atomic.h>
struct unwind_cache {
unsigned long unwind_completed;
@@ -32,7 +33,7 @@ union unwind_task_id {
};
struct unwind_task_info {
unsigned long unwind_mask;
atomic_long_t unwind_mask;
struct unwind_cache *cache;
struct callback_head work;
union unwind_task_id id;

17
kernel/unwind/deferred.c
View File

@@ -53,7 +53,7 @@ DEFINE_STATIC_SRCU(unwind_srcu);
static inline bool unwind_pending(struct unwind_task_info *info)
{
return test_bit(UNWIND_PENDING_BIT, &info->unwind_mask);
return atomic_long_read(&info->unwind_mask) & UNWIND_PENDING;
}
/*
@@ -141,7 +141,7 @@ int unwind_user_faultable(struct unwind_stacktrace *trace)
cache->nr_entries = trace->nr;
/* Clear nr_entries on way back to user space */
set_bit(UNWIND_USED_BIT, &info->unwind_mask);
atomic_long_or(UNWIND_USED, &info->unwind_mask);
return 0;
}
@@ -159,7 +159,7 @@ static void process_unwind_deferred(struct task_struct *task)
/* Clear pending bit but make sure to have the current bits */
bits = atomic_long_fetch_andnot(UNWIND_PENDING,
(atomic_long_t *)&info->unwind_mask);
&info->unwind_mask);
/*
* From here on out, the callback must always be called, even if it's
* just an empty trace.
@@ -264,7 +264,7 @@ int unwind_deferred_request(struct unwind_work *work, u64 *cookie)
*cookie = get_cookie(info);
old = READ_ONCE(info->unwind_mask);
old = atomic_long_read(&info->unwind_mask);
/* Is this already queued or executed */
if (old & bit)
@@ -277,7 +277,7 @@ int unwind_deferred_request(struct unwind_work *work, u64 *cookie)
* to have a callback.
*/
bits = UNWIND_PENDING | bit;
old = atomic_long_fetch_or(bits, (atomic_long_t *)&info->unwind_mask);
old = atomic_long_fetch_or(bits, &info->unwind_mask);
if (old & bits) {
/*
* If the work's bit was set, whatever set it had better
@@ -291,7 +291,7 @@ int unwind_deferred_request(struct unwind_work *work, u64 *cookie)
ret = task_work_add(current, &info->work, twa_mode);
if (WARN_ON_ONCE(ret))
WRITE_ONCE(info->unwind_mask, 0);
atomic_long_set(&info->unwind_mask, 0);
return ret;
}
@@ -323,7 +323,8 @@ void unwind_deferred_cancel(struct unwind_work *work)
guard(rcu)();
/* Clear this bit from all threads */
for_each_process_thread(g, t) {
clear_bit(bit, &t->unwind_info.unwind_mask);
atomic_long_andnot(BIT(bit),
&t->unwind_info.unwind_mask);
if (t->unwind_info.cache)
clear_bit(bit, &t->unwind_info.cache->unwind_completed);
}
@@ -353,7 +354,7 @@ 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;
atomic_long_set(&info->unwind_mask, 0);
}
void unwind_task_free(struct task_struct *task)