Messages in this thread | | | Subject | net/sched: latent livelock in dev_deactivate_many() due to yield() usage | From | Mike Galbraith <> | Date | Sun, 02 Apr 2017 06:28:41 +0200 |
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Greetings network wizards,
Quoting kernel/sched/core.c: /** * yield - yield the current processor to other threads. * * Do not ever use this function, there's a 99% chance you're doing it wrong. * * The scheduler is at all times free to pick the calling task as the most * eligible task to run, if removing the yield() call from your code breaks * it, its already broken. * * Typical broken usage is: * * while (!event) * yield(); * * where one assumes that yield() will let 'the other' process run that will * make event true. If the current task is a SCHED_FIFO task that will never * happen. Never use yield() as a progress guarantee!! * * If you want to use yield() to wait for something, use wait_event(). * If you want to use yield() to be 'nice' for others, use cond_resched(). * If you still want to use yield(), do not! */
Livelock can be triggered by setting kworkers to SCHED_FIFO, then suspend/resume.. you come back from sleepy-land with a spinning kworker. For whatever reason, I can only do that with an enterprise like config, my standard config refuses to play, but no matter, it's "Typical broken usage".
(yield() should be rendered dead)
-Mike
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