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unwind: Finish up unwind when a task exits

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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.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Indu Bhagat <indu.bhagat@oracle.com>
Cc: "Jose E. Marchesi" <jemarch@gnu.org>
Cc: Beau Belgrave <beaub@linux.microsoft.com>
Cc: Jens Remus <jremus@linux.ibm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Florian Weimer <fweimer@redhat.com>
Cc: Sam James <sam@gentoo.org>
Link: https://lore.kernel.org/20250729182406.504259474@kernel.org
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt 2025-07-29 14:23:14 -04:00 committed by Steven Rostedt (Google)
parent 357eda2d74
commit b3b9cb11aa
3 changed files with 25 additions and 3 deletions
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3
include/linux/unwind_deferred.h
View File

@ -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); int unwind_deferred_request(struct unwind_work *work, u64 *cookie);
void unwind_deferred_cancel(struct unwind_work *work); 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) static __always_inline void unwind_reset_info(void)
{ {
struct unwind_task_info *info = &current->unwind_info; struct unwind_task_info *info = &current->unwind_info;
@ -71,6 +73,7 @@ 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 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_cancel(struct unwind_work *work) {}
static inline void unwind_deferred_task_exit(struct task_struct *task) {}
static inline void unwind_reset_info(void) {} static inline void unwind_reset_info(void) {}
#endif /* !CONFIG_UNWIND_USER */ #endif /* !CONFIG_UNWIND_USER */

2
kernel/exit.c
View File

@ -68,6 +68,7 @@
#include <linux/rethook.h> #include <linux/rethook.h>
#include <linux/sysfs.h> #include <linux/sysfs.h>
#include <linux/user_events.h> #include <linux/user_events.h>
#include <linux/unwind_deferred.h>
#include <linux/uaccess.h> #include <linux/uaccess.h>
#include <linux/pidfs.h> #include <linux/pidfs.h>
@ -938,6 +939,7 @@ void __noreturn do_exit(long code)
tsk->exit_code = code; tsk->exit_code = code;
taskstats_exit(tsk, group_dead); taskstats_exit(tsk, group_dead);
unwind_deferred_task_exit(tsk);
trace_sched_process_exit(tsk, group_dead); trace_sched_process_exit(tsk, group_dead);
/* /*

23
kernel/unwind/deferred.c
View File

@ -114,7 +114,7 @@ int unwind_user_faultable(struct unwind_stacktrace *trace)
/* Should always be called from faultable context */ /* Should always be called from faultable context */
might_fault(); might_fault();
if (current->flags & PF_EXITING) if (!current->mm)
return -EINVAL; return -EINVAL;
if (!info->cache) { if (!info->cache) {
@ -147,9 +147,9 @@ int unwind_user_faultable(struct unwind_stacktrace *trace)
return 0; 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_stacktrace trace;
struct unwind_work *work; struct unwind_work *work;
unsigned long bits; unsigned long bits;
@ -186,6 +186,23 @@ static void unwind_deferred_task_work(struct callback_head *head)
} }
} }
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 = &current->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 kernel exit * unwind_deferred_request - Request a user stacktrace on task kernel exit
* @work: Unwind descriptor requesting the trace * @work: Unwind descriptor requesting the trace