preempt & ne2k
Hi!
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testing the patch complaining about, AND one that seems like it could be addressed by using IRQ disabling as a latency guard in addition to spinlocks.
I dont believe anyone has tested the driver hard with pre-empt. Its not that this driver can't be fixed. Its that this is one tiny example of maybe thousands of other similar flaws lurking. There is no obvious automated way to find them either.
So.... you have shown performance problem in one driver. Maybe *bad* performance problem, but only performance problem. There may be other performance problems out there. And what?
Pavel
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When do you have heart between your knees?
Quoted 11 lines · Pavel Machek
Hi!
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testing the patch complaining about, AND one that seems like it could be addressed by using IRQ disabling as a latency guard in addition to spinlocks.
I dont believe anyone has tested the driver hard with pre-empt. Its not that this driver can't be fixed. Its that this is one tiny example of maybe thousands of other similar flaws lurking. There is no obvious automated way to find them either.
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So.... you have shown performance problem in one driver. Maybe *bad* performance problem, but only performance problem. There may be other performance problems out there. And what?
Pavel
In Alans example it is not a performance problem - it is more of a correctness problem.
The case when a driver were disabling a specific interrupt was not handled in a 100% correct way.
There are some other cases that might be even harder to detect - disabling from a device by writing in its control register.
But if the preempt patch is added those critical sections can be protected.
It is not trivial nor impossible...
/RogerL
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Roger Larsson Skellefteå Sweden