Re: [RESEND][PATCH v15 0/4] perf: Support the deferred unwinding infrastructure
From: Peter Zijlstra <peterz@infradead.org>
Date: 2025-09-18 11:46:23
Also in:
bpf, lkml
Subsystem:
the rest, userspace stack unwinding · Maintainers:
Linus Torvalds, Josh Poimboeuf, Steven Rostedt
So I started looking at this, but given I never seen the deferred unwind bits that got merged I have to look at that first. Headers want something like so.. Let me read the rest. --- include/linux/unwind_deferred.h | 38 +++++++++++++++++++---------------- include/linux/unwind_deferred_types.h | 2 ++ 2 files changed, 23 insertions(+), 17 deletions(-)
diff --git a/include/linux/unwind_deferred.h b/include/linux/unwind_deferred.h
index 26122d00708a..5d51a3f2f8ec 100644
--- a/include/linux/unwind_deferred.h
+++ b/include/linux/unwind_deferred.h@@ -8,7 +8,8 @@ struct unwind_work; -typedef void (*unwind_callback_t)(struct unwind_work *work, struct unwind_stacktrace *trace, u64 cookie); +typedef void (*unwind_callback_t)(struct unwind_work *work, + struct unwind_stacktrace *trace, u64 cookie); struct unwind_work { struct list_head list;
@@ -44,22 +45,22 @@ void unwind_deferred_task_exit(struct task_struct *task); static __always_inline void unwind_reset_info(void) { struct unwind_task_info *info = ¤t->unwind_info; - unsigned long bits; + unsigned long bits = info->unwind_mask; /* Was there any unwinding? */ - if (unlikely(info->unwind_mask)) { - bits = info->unwind_mask; - do { - /* Is a task_work going to run again before going back */ - if (bits & UNWIND_PENDING) - return; - } while (!try_cmpxchg(&info->unwind_mask, &bits, 0UL)); - current->unwind_info.id.id = 0; + if (likely(!bits)) + return; - if (unlikely(info->cache)) { - info->cache->nr_entries = 0; - info->cache->unwind_completed = 0; - } + do { + /* Is a task_work going to run again before going back */ + if (bits & UNWIND_PENDING) + return; + } while (!try_cmpxchg(&info->unwind_mask, &bits, 0UL)); + current->unwind_info.id.id = 0; + + if (unlikely(info->cache)) { + info->cache->nr_entries = 0; + info->cache->unwind_completed = 0; } }
@@ -68,9 +69,12 @@ static __always_inline void unwind_reset_info(void) static inline void unwind_task_init(struct task_struct *task) {} static inline void unwind_task_free(struct task_struct *task) {} -static inline int unwind_user_faultable(struct unwind_stacktrace *trace) { return -ENOSYS; } -static inline int unwind_deferred_init(struct unwind_work *work, unwind_callback_t func) { return -ENOSYS; } -static inline int unwind_deferred_request(struct unwind_work *work, u64 *timestamp) { return -ENOSYS; } +static inline int unwind_user_faultable(struct unwind_stacktrace *trace) +{ return -ENOSYS; } +static inline int unwind_deferred_init(struct unwind_work *work, unwind_callback_t func) +{ return -ENOSYS; } +static inline int unwind_deferred_request(struct unwind_work *work, u64 *timestamp) +{ return -ENOSYS; } static inline void unwind_deferred_cancel(struct unwind_work *work) {} static inline void unwind_deferred_task_exit(struct task_struct *task) {}
diff --git a/include/linux/unwind_deferred_types.h b/include/linux/unwind_deferred_types.h
index 33b62ac25c86..29452ff49859 100644
--- a/include/linux/unwind_deferred_types.h
+++ b/include/linux/unwind_deferred_types.h@@ -2,6 +2,8 @@ #ifndef _LINUX_UNWIND_USER_DEFERRED_TYPES_H #define _LINUX_UNWIND_USER_DEFERRED_TYPES_H +#include <linux/types.h> + struct unwind_cache { unsigned long unwind_completed; unsigned int nr_entries;