Re: [RFC PATCH 0/6] Convert all tasklets to workqueues

[Oleg Nesterov <oleg@tv-sign.ru>]

On 06/29, Oleg Nesterov wrote:
>
> Suppose we have the tasklets T1 and T2, both are scheduled on the
> same CPU. T1 takes some spinlock LOCK.
> 
> Currently it is possible to do
> 
> 	spin_lock(LOCK);
> 	disable_tasklet(T2);
> 
> With this patch, the above code hangs.

I am stupid. Yes, flush_workqueue() is evil and should not be used, but
if we use workqueues, tasklet_disable() becomes might_sleep() anyway.
This is incompatible and unavoidable change.

grep, grep...

	net/bluetooth/hci_core.c:hci_rx_task()

		read_lock(&hci_task_lock)
		hci_event_packet()
			hci_num_comp_pkts_evt()
				tasklet_disable(&hdev->tx_task)

Oleg.

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