Hi,
I am working on a wireless driver. It seems to deadlock
on flush_scheduled_work while iface is being downed.
I've put debug printks in code:
static void
acx_s_down(netdevice_t *dev)
{
wlandevice_t *priv = acx_netdev_priv(dev);
unsigned long flags;
FN_ENTER;
printk("acx_s_down: stop_queue\n");
acx_stop_queue(dev, "during close");
/* we really don't want to have an asynchronous tasklet disturb us
* after something vital for its job has been shut down, so
* end all remaining work now... */
printk("acx_s_down: set_status\n");
acx_set_status(priv, ACX_STATUS_0_STOPPED);
printk("acx_s_down: flush_scheduled_work\n");
flush_scheduled_work();
/* kernel/timer.c says it's illegal to del_timer_sync()
** a timer which restarts itself. We guarantee this cannot
** ever happen because acx_i_timer() never does this if
** status is ACX_STATUS_0_STOPPED
*/
printk("acx_s_down: del_timer_sync\n");
del_timer_sync(&priv->mgmt_timer);
...
"acx_s_down: del_timer_sync" never appears.
I verified that work function never gets called because it has
debug prints also:
static void
acx_e_after_interrupt_task(void *data)
{
netdevice_t *dev = (netdevice_t *) data;
wlandevice_t *priv;
FN_ENTER;
priv = (struct wlandevice *) dev->priv;
/* Avoid deadlock - FLUSH_SCHEDULED_WORK()
** is called under sem and it waits for any
** already submitted work to complete! */
if (priv->status == ACX_STATUS_0_STOPPED) {
printk("acx_e_after_interrupt_task: deadlock avoided\n");
FN_EXIT0;
return;
}
and I don't see them.
kernel log:
...
20:45:50 kernel: 015c3e6a ==> acx_e_close
20:45:50 kernel: 015c3e6c ==> acx_s_down
20:45:50 kernel: acx_s_down: stop_queue
20:45:50 kernel: tx: stop queue during close
20:45:50 kernel: acx_s_down: set_status
20:45:50 kernel: 015c3e79 ==> acx_set_status
20:45:50 kernel: acx_set_status(0):STOPPED
20:45:50 kernel: tx: carrier off after losing association
20:45:50 kernel: tx: stop queue after losing association
20:45:50 kernel: 015c3e82 <== acx_set_status
20:45:50 kernel: acx_s_down: flush_scheduled_work
20:45:50 kernel: SysRq : Changing Loglevel
20:45:50 kernel: Loglevel set to 0
20:45:50 kernel: 015c3ebb ==> acx_i_interrupt
20:45:50 kernel: IRQ type:0000, mask:D9F5 - all are masked, IRQ_NONE
20:45:50 kernel: 015c3ebb <== acx_i_interrupt
20:45:50 kernel: 015c3ebb ==> acx_i_interrupt
20:45:50 kernel: IRQ type:0000, mask:D9F5 - all are masked, IRQ_NONE
20:45:50 kernel: 015c3ebb <== acx_i_interrupt
...
acx_i_interrupt lines indicate that interrupts still are serviced
(because we are on shared IRQ line), but as you can see, neither
"acx_s_down: del_timer_sync" nor "acx_e_after_interrupt_task: deadlock avoided"
appears after "acx_s_down: flush_scheduled_work"
Why?!
NB: acx_s_down is called under semaphore.
--
vda
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