7 Nov
2016
7 Nov
'16
4:40 p.m.
Alan Young wrote:
On 07/11/16 14:15, Clemens Ladisch wrote:
Alan Young wrote:
It is possible that the DMA interrupt handler could call snd_pcm_update_hw_ptr0() while it is part way through a call from snd_pcm_status(), or vice versa?
The *lock_irq* functions disable interrupts on the current CPU.
But only on the current CPU? So that would imply that multiple threads could execute snd_pcm_update_hw_ptr0() simultaneously on multi-CPU systems.
That's what the lock is for.
I presume that the interrupt handler cannot be pre-empted by a user- space call such as snd_pcm_status().
During execution of an interrupt handler, interrupts also are disabled.
Regards, Clemens