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| author | Avi Kivity <avi@redhat.com> | 2009-11-29 16:34:48 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2009-11-29 22:03:04 +0100 |
| commit | 8e7cac79808b62f242069a6ac88d364d35621371 (patch) | |
| tree | b68dacc4e080ec8c4587d783a8014906e2eb2445 /kernel/fork.c | |
| parent | 3c912b6edaac56cb451e7571c95c15cbb6bd0c81 (diff) | |
| download | lwn-8e7cac79808b62f242069a6ac88d364d35621371.tar.gz lwn-8e7cac79808b62f242069a6ac88d364d35621371.zip | |
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>
Diffstat (limited to 'kernel/fork.c')
| -rw-r--r-- | kernel/fork.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/kernel/fork.c b/kernel/fork.c index 266c6af6ef1b..1b7512d5a64a 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 */ |