linux-stable/include/linux/user-return-notifier.h
Avi Kivity 8e7cac7980 core: Fix user return notifier on fork()
fork() clones all thread_info flags, including
TIF_USER_RETURN_NOTIFY; if the new task is first scheduled on a cpu
which doesn't have user return notifiers set, this causes user
return notifiers to trigger without any way of clearing itself.

This is easy to trigger with a forky workload on the host in
parallel with kvm, resulting in a cpu in an endless loop on the
verge of returning to userspace.

Fix by dropping the TIF_USER_RETURN_NOTIFY immediately after fork.

Signed-off-by: Avi Kivity <avi@redhat.com>
LKML-Reference: <1259505288-16559-1-git-send-email-avi@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
2009-11-29 22:03:04 +01:00

49 lines
1.1 KiB
C

#ifndef _LINUX_USER_RETURN_NOTIFIER_H
#define _LINUX_USER_RETURN_NOTIFIER_H
#ifdef CONFIG_USER_RETURN_NOTIFIER
#include <linux/list.h>
#include <linux/sched.h>
struct user_return_notifier {
void (*on_user_return)(struct user_return_notifier *urn);
struct hlist_node link;
};
void user_return_notifier_register(struct user_return_notifier *urn);
void user_return_notifier_unregister(struct user_return_notifier *urn);
static inline void propagate_user_return_notify(struct task_struct *prev,
struct task_struct *next)
{
if (test_tsk_thread_flag(prev, TIF_USER_RETURN_NOTIFY)) {
clear_tsk_thread_flag(prev, TIF_USER_RETURN_NOTIFY);
set_tsk_thread_flag(next, TIF_USER_RETURN_NOTIFY);
}
}
void fire_user_return_notifiers(void);
static inline void clear_user_return_notifier(struct task_struct *p)
{
clear_tsk_thread_flag(p, TIF_USER_RETURN_NOTIFY);
}
#else
struct user_return_notifier {};
static inline void propagate_user_return_notify(struct task_struct *prev,
struct task_struct *next)
{
}
static inline void fire_user_return_notifiers(void) {}
static inline void clear_user_return_notifier(struct task_struct *p) {}
#endif
#endif