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