Messages in this thread | | | Date | Mon, 1 Aug 2011 11:46:37 -0400 | From | Josh Boyer <> | Subject | 3.0-git15 Atomic scheduling in pidmap_init |
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We're seeing a scheduling while atomic backtrace in rawhide from pidmap_init (https://bugzilla.redhat.com/show_bug.cgi?id=726877). While this seems mostly harmless given that there isn't anything else to schedule to at this point, I do wonder why things are marked as needing rescheduled so early.
We get to might_sleep through the might_sleep_if call in slab_pre_alloc_hook because both kzalloc and KMEM_CACHE are called with GFP_KERNEL. That eventually has a call chain like:
might_resched->_cond_resched->should_resched
which apparently returns true. Why the initial thread says it should reschedule at this point, I'm not sure.
I tried cheating by making the kzalloc call in pidmap_init use GFP_IOFS instead of GFP_KERNEL to avoid the might_sleep_if call, and that worked but I can't do the same for the kmalloc calls in kmem_cache_create, so getting to the bottom of why should_resched is returning true seems to be a better approach.
josh
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