Re: [PATCH v2 7/9] sched: define TIF_ALLOW_RESCHED

Thomas Gleixner
2023-10-02T16:13:47Z

On Mon, Oct 02 2023 at 10:15, Steven Rostedt wrote:
> On Sat, 23 Sep 2023 03:11:05 +0200
> Thomas Gleixner <tglx@linutronix.de> wrote:
>
>> Though definitely I'm putting a permanent NAK in place for any attempts
>> to duct tape the preempt=NONE model any further by sprinkling more
>> cond*() and whatever warts around.
>
> Well, until we have this fix in, we will still need to sprinkle those
> around when they are triggering watchdog timeouts. I just had to add one
> recently due to a timeout report :-(

cond_resched() sure. But not new flavours of it, like the
[dis]allow_resched() which sparked this discussion.

>> - TRACE_FLAG_NEED_RESCHED = 0x04,
>> + TRACE_FLAG_NEED_RESCHED = 0x02,
>> + TRACE_FLAG_NEED_RESCHED_LAZY = 0x04,
>
> Is LAZY only used for PREEMPT_NONE? Or do we use it for CONFIG_PREEMPT?
> Because, NEED_RESCHED is known, and moving that to bit 2 will break user
> space. Having LAZY replace the IRQS_NOSUPPORT will cause the least
> "breakage".

Either way works for me.

Thanks,

tglx