Commit-ID: 8e7cac79808b62f242069a6ac88d364d35621371 Gitweb: http://git.kernel.org/tip/8e7cac79808b62f242069a6ac88d364d35621371 Author: Avi Kivity <avi@xxxxxxxxxx> AuthorDate: Sun, 29 Nov 2009 16:34:48 +0200 Committer: Ingo Molnar <mingo@xxxxxxx> CommitDate: Sun, 29 Nov 2009 22:03:04 +0100 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@xxxxxxxxxx> LKML-Reference: <1259505288-16559-1-git-send-email-avi@xxxxxxxxxx> Signed-off-by: Ingo Molnar <mingo@xxxxxxx> --- include/linux/user-return-notifier.h | 7 +++++++ kernel/fork.c | 2 ++ 2 files changed, 9 insertions(+), 0 deletions(-) diff --git a/include/linux/user-return-notifier.h b/include/linux/user-return-notifier.h index b6ac056..9c4a445 100644 --- a/include/linux/user-return-notifier.h +++ b/include/linux/user-return-notifier.h @@ -26,6 +26,11 @@ static inline void propagate_user_return_notify(struct task_struct *prev, 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 {}; @@ -37,6 +42,8 @@ static inline void propagate_user_return_notify(struct task_struct *prev, static inline void fire_user_return_notifiers(void) {} +static inline void clear_user_return_notifier(struct task_struct *p) {} + #endif #endif diff --git a/kernel/fork.c b/kernel/fork.c index 266c6af..1b7512d 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -64,6 +64,7 @@ #include <linux/magic.h> #include <linux/perf_event.h> #include <linux/posix-timers.h> +#include <linux/user-return-notifier.h> #include <asm/pgtable.h> #include <asm/pgalloc.h> @@ -249,6 +250,7 @@ static struct task_struct *dup_task_struct(struct task_struct *orig) goto out; setup_thread_stack(tsk, orig); + clear_user_return_notifier(tsk); stackend = end_of_stack(tsk); *stackend = STACK_END_MAGIC; /* for overflow detection */ -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html