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From:   Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To:     Davidlohr Bueso <dave@stgolabs.net>
Cc:     linux-scsi@vger.kernel.org, martin.petersen@oracle.com,
        ejb@linux.ibm.com, tglx@linutronix.de
Subject: Re: [PATCH 00/10] scsi: Replace tasklets as BH
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References: <20220530231512.9729-1-dave@stgolabs.net>
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On 2022-05-30 16:15:02 [-0700], Davidlohr Bueso wrote:
> and thus are more important than all tasks on the system. Furthermore
> there are no guarantees it will run in irq context at all if ksoftirq
> kicks in.

They never run in IRQ context, they always run in softirq context. Even
if ksoftirqd kicks in, the callbacks (tasklets) are invoked in softirq
context.
That is sort of preemptible but in tasklet's case it will run/ complete
all callbacks before any kind of preemption can kick in.
So there is the lack of preemption for many/ long running callbacks and
the callbacks have no context/ owner which means there is no way of
preferring one over the other.

Sebastian