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| author | Mike Christie <michael.christie@oracle.com> | 2023-06-07 14:23:38 -0500 |
|---|---|---|
| committer | Michael S. Tsirkin <mst@redhat.com> | 2023-06-08 15:43:09 -0400 |
| commit | 4b13cbef797048fbb525f8c635a5279e9d209d93 (patch) | |
| tree | 59de4d4c9dc49411fe09d36c1390f58f08e7ad36 /kernel/vhost_task.c | |
| parent | a284f09effea1908db7985dbfb5458c9100038d8 (diff) | |
| download | lwn-4b13cbef797048fbb525f8c635a5279e9d209d93.tar.gz lwn-4b13cbef797048fbb525f8c635a5279e9d209d93.zip | |
vhost: Fix worker hangs due to missed wake up calls
We can race where we have added work to the work_list, but
vhost_task_fn has passed that check but not yet set us into
TASK_INTERRUPTIBLE. wake_up_process will see us in TASK_RUNNING and
just return.
This bug was intoduced in commit f9010dbdce91 ("fork, vhost: Use
CLONE_THREAD to fix freezer/ps regression") when I moved the setting
of TASK_INTERRUPTIBLE to simplfy the code and avoid get_signal from
logging warnings about being in the wrong state. This moves the setting
of TASK_INTERRUPTIBLE back to before we test if we need to stop the
task to avoid a possible race there as well. We then have vhost_worker
set TASK_RUNNING if it finds work similar to before.
Fixes: f9010dbdce91 ("fork, vhost: Use CLONE_THREAD to fix freezer/ps regression")
Signed-off-by: Mike Christie <michael.christie@oracle.com>
Message-Id: <20230607192338.6041-3-michael.christie@oracle.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Diffstat (limited to 'kernel/vhost_task.c')
| -rw-r--r-- | kernel/vhost_task.c | 16 |
1 files changed, 9 insertions, 7 deletions
diff --git a/kernel/vhost_task.c b/kernel/vhost_task.c index f80d5c51ae67..da35e5b7f047 100644 --- a/kernel/vhost_task.c +++ b/kernel/vhost_task.c @@ -28,10 +28,6 @@ static int vhost_task_fn(void *data) for (;;) { bool did_work; - /* mb paired w/ vhost_task_stop */ - if (test_bit(VHOST_TASK_FLAGS_STOP, &vtsk->flags)) - break; - if (!dead && signal_pending(current)) { struct ksignal ksig; /* @@ -48,11 +44,17 @@ static int vhost_task_fn(void *data) clear_thread_flag(TIF_SIGPENDING); } + /* mb paired w/ vhost_task_stop */ + set_current_state(TASK_INTERRUPTIBLE); + + if (test_bit(VHOST_TASK_FLAGS_STOP, &vtsk->flags)) { + __set_current_state(TASK_RUNNING); + break; + } + did_work = vtsk->fn(vtsk->data); - if (!did_work) { - set_current_state(TASK_INTERRUPTIBLE); + if (!did_work) schedule(); - } } complete(&vtsk->exited); |