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8e7cac7980
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>
50 lines
1.1 KiB
C
50 lines
1.1 KiB
C
#ifndef _LINUX_USER_RETURN_NOTIFIER_H
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#define _LINUX_USER_RETURN_NOTIFIER_H
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#ifdef CONFIG_USER_RETURN_NOTIFIER
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#include <linux/list.h>
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#include <linux/sched.h>
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struct user_return_notifier {
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void (*on_user_return)(struct user_return_notifier *urn);
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struct hlist_node link;
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};
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void user_return_notifier_register(struct user_return_notifier *urn);
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void user_return_notifier_unregister(struct user_return_notifier *urn);
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static inline void propagate_user_return_notify(struct task_struct *prev,
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struct task_struct *next)
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{
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if (test_tsk_thread_flag(prev, TIF_USER_RETURN_NOTIFY)) {
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clear_tsk_thread_flag(prev, TIF_USER_RETURN_NOTIFY);
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set_tsk_thread_flag(next, TIF_USER_RETURN_NOTIFY);
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}
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}
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void fire_user_return_notifiers(void);
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static inline void clear_user_return_notifier(struct task_struct *p)
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{
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clear_tsk_thread_flag(p, TIF_USER_RETURN_NOTIFY);
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}
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#else
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struct user_return_notifier {};
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static inline void propagate_user_return_notify(struct task_struct *prev,
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struct task_struct *next)
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{
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}
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static inline void fire_user_return_notifiers(void) {}
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static inline void clear_user_return_notifier(struct task_struct *p) {}
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#endif
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#endif
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