diff options
| author | Jesper Dangaard Brouer <brouer@redhat.com> | 2017-10-23 19:39:28 +0200 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2017-10-24 18:40:22 +0900 |
| commit | 31749468c3f9d77927ed3144259dc208e6625ede (patch) | |
| tree | 33d083824b454cd344121d6ef8ed2ac1d37afeb4 /kernel/bpf/cpumap.c | |
| parent | 7f6b437e9b82a6d702a7f8f75c83ffdec6e03c54 (diff) | |
| download | linux-31749468c3f9d77927ed3144259dc208e6625ede.tar.gz | |
bpf: cpumap fix potential lost wake-up problem
As pointed out by Michael, commit 1c601d829ab0 ("bpf: cpumap xdp_buff
to skb conversion and allocation") contains a classical example of the
potential lost wake-up problem.
We need to recheck the condition __ptr_ring_empty() after changing
current->state to TASK_INTERRUPTIBLE, this avoids a race between
wake_up_process() and schedule(). After this, a race with
wake_up_process() will simply change the state to TASK_RUNNING, and
the schedule() call not really put us to sleep.
Fixes: 1c601d829ab0 ("bpf: cpumap xdp_buff to skb conversion and allocation")
Reported-by: "Michael S. Tsirkin" <mst@redhat.com>
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'kernel/bpf/cpumap.c')
| -rw-r--r-- | kernel/bpf/cpumap.c | 12 |
1 files changed, 8 insertions, 4 deletions
diff --git a/kernel/bpf/cpumap.c b/kernel/bpf/cpumap.c index b4358d84ddf1..86e29cbf7827 100644 --- a/kernel/bpf/cpumap.c +++ b/kernel/bpf/cpumap.c @@ -288,13 +288,17 @@ static int cpu_map_kthread_run(void *data) /* Release CPU reschedule checks */ if (__ptr_ring_empty(rcpu->queue)) { - __set_current_state(TASK_INTERRUPTIBLE); - schedule(); - sched = 1; + set_current_state(TASK_INTERRUPTIBLE); + /* Recheck to avoid lost wake-up */ + if (__ptr_ring_empty(rcpu->queue)) { + schedule(); + sched = 1; + } else { + __set_current_state(TASK_RUNNING); + } } else { sched = cond_resched(); } - __set_current_state(TASK_RUNNING); /* Process packets in rcpu->queue */ local_bh_disable(); |