[PATCH v13 12/14] unwind: Finish up unwind when a task exits
From: Steven Rostedt <rostedt@kernel.org>
Date: 2025-07-08 01:23:59
Also in:
bpf, lkml
Subsystem:
the rest, userspace stack unwinding · Maintainers:
Linus Torvalds, Josh Poimboeuf, Steven Rostedt
From: Steven Rostedt <rostedt@goodmis.org> On do_exit() when a task is exiting, if a unwind is requested and the deferred user stacktrace is deferred via the task_work, the task_work callback is called after exit_mm() is called in do_exit(). This means that the user stack trace will not be retrieved and an empty stack is created. Instead, add a function unwind_deferred_task_exit() and call it just before exit_mm() so that the unwinder can call the requested callbacks with the user space stack. Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> --- include/linux/unwind_deferred.h | 3 +++ kernel/exit.c | 2 ++ kernel/unwind/deferred.c | 23 ++++++++++++++++++++--- 3 files changed, 25 insertions(+), 3 deletions(-)
diff --git a/include/linux/unwind_deferred.h b/include/linux/unwind_deferred.h
index 376bfd50ff75..a9d5b100d6b2 100644
--- a/include/linux/unwind_deferred.h
+++ b/include/linux/unwind_deferred.h@@ -39,6 +39,8 @@ int unwind_deferred_init(struct unwind_work *work, unwind_callback_t func); int unwind_deferred_request(struct unwind_work *work, u64 *cookie); void unwind_deferred_cancel(struct unwind_work *work); +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;
@@ -69,6 +71,7 @@ static inline int unwind_deferred_init(struct unwind_work *work, unwind_callback 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) {} static inline void unwind_reset_info(void) {} #endif /* !CONFIG_UNWIND_USER */
diff --git a/kernel/exit.c b/kernel/exit.c
index bb184a67ac73..1d8c8ac33c4f 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c@@ -68,6 +68,7 @@ #include <linux/rethook.h> #include <linux/sysfs.h> #include <linux/user_events.h> +#include <linux/unwind_deferred.h> #include <linux/uaccess.h> #include <linux/pidfs.h>
@@ -938,6 +939,7 @@ void __noreturn do_exit(long code) tsk->exit_code = code; taskstats_exit(tsk, group_dead); + unwind_deferred_task_exit(tsk); trace_sched_process_exit(tsk, group_dead); /*
diff --git a/kernel/unwind/deferred.c b/kernel/unwind/deferred.c
index 9299974b6562..039e12700d49 100644
--- a/kernel/unwind/deferred.c
+++ b/kernel/unwind/deferred.c@@ -113,7 +113,7 @@ int unwind_user_faultable(struct unwind_stacktrace *trace) /* Should always be called from faultable context */ might_fault(); - if (current->flags & PF_EXITING) + if (!current->mm) return -EINVAL; if (!info->cache) {
@@ -146,9 +146,9 @@ int unwind_user_faultable(struct unwind_stacktrace *trace) return 0; } -static void unwind_deferred_task_work(struct callback_head *head) +static void process_unwind_deferred(struct task_struct *task) { - struct unwind_task_info *info = container_of(head, struct unwind_task_info, work); + struct unwind_task_info *info = &task->unwind_info; struct unwind_stacktrace trace; struct unwind_work *work; unsigned long bits;
@@ -183,6 +183,23 @@ static void unwind_deferred_task_work(struct callback_head *head) srcu_read_unlock(&unwind_srcu, idx); } +static void unwind_deferred_task_work(struct callback_head *head) +{ + process_unwind_deferred(current); +} + +void unwind_deferred_task_exit(struct task_struct *task) +{ + struct unwind_task_info *info = ¤t->unwind_info; + + if (!unwind_pending(info)) + return; + + process_unwind_deferred(task); + + task_work_cancel(task, &info->work); +} + /** * unwind_deferred_request - Request a user stacktrace on task exit * @work: Unwind descriptor requesting the trace
--
2.47.2