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The should_preempt() code was catching some of the "unrunnable" cases
but not all of them, opening the possibility of failing to preempt a
just-pended thread and thus waking it up synchronously. There are
reports of this causing spin loops over k_poll() in the network stack
work queues (see #8049).
Note that the previous _is_dummy() call is folded into (the somewhat
verbosely named) _is_thread_prevented_from_running(), and that the
order of tests has been changed/optimized to hopefully catch common
cases earlier.
The should_preempt() code was catching some of the "unrunnable" cases
but not all of them, opening the possibility of failing to preempt a
just-pended thread and thus waking it up synchronously. There are
reports of this causing spin loops over k_poll() in the network stack
work queues (see zephyrproject-rtos#8049).
Note that the previous _is_dummy() call is folded into (the somewhat
verbosely named) _is_thread_prevented_from_running(), and that the
order of tests has been changed/optimized to hopefully catch common
cases earlier.
Suggested-by: Michael Scott <michael@opensourcefoundries.com>
Signed-off-by: Andy Ross <andrew.j.ross@intel.com>
This code actually is performance-critical, though this close to release I'd prefer to keep this clearer rather than optimized. Scheduler performance is an item for 1.13 for sure (we've regressed a bit, though this patch turns out to repair most of the damage). In this case though I'd expect the compiler to have figured out the proper boolean path here. Note that both _is_idle() and is_preempt() are comparisons on the thread priority, so it might be able to fold them together.
Yeah, I just did a dumb local check. GCC always simplifies the non-SMP return thread == _idle_thread case, but the SMP case is a bit trickier. I don't know the context here though. Just something random I spotted.
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andyross
requested review from
lpereira,
mike-scott,
ramakrishnapallala and
jukkar
The should_preempt() code was catching some of the "unrunnable" cases
but not all of them, opening the possibility of failing to preempt a
just-pended thread and thus waking it up synchronously. There are
reports of this causing spin loops over k_poll() in the network stack
work queues (see #8049).
Note that the previous _is_dummy() call is folded into (the somewhat
verbosely named) _is_thread_prevented_from_running(), and that the
order of tests has been changed/optimized to hopefully catch common
cases earlier.
Fixes #8049
Suggested-by: Michael Scott michael@opensourcefoundries.com
Signed-off-by: Andy Ross andrew.j.ross@intel.com