Messages in this thread | | | Date | Fri, 12 Jun 2009 18:05:47 +0300 | From | Pekka Enberg <> | Subject | Re: [PATCH v2] slab,slub: ignore __GFP_WAIT if we're booting or suspending |
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Hi Linus,
Linus Torvalds wrote: > > On Fri, 12 Jun 2009, Pekka J Enberg wrote: >> >> + if (system_state != SYSTEM_RUNNING) >> + local_flags &= ~__GFP_WAIT; >> + >> + might_sleep_if(local_flags & __GFP_WAIT); > > This is pointless. > > You're doing the "might_sleep_if()" way too late. At that point, you've > already lost 99% of all coverage, since now none of the cases of just > finding a free slab entry on the list will ever trigger that > "might_sleep()" case. > > So you need to do this _early_, at the entry-point, not late, at cache > re-fill time. > > So rather than removing the might_sleep_if() at the early point, and then > moving it to this late stage (because you only do the local_flags fixups > late), you need to move the local-flags fixup early instead, and do the > might_sleep_it() there. > > The whole point of "might_sleep()" is that it triggers every time if > something is called in the wrong context - not just for the cases where it > actually _does_ sleep.
OK, makes sense. So what do you think of this patch then:
http://patchwork.kernel.org/patch/29733/
It's what Ben has been proposing all along in a slightly edited form.
Pekka
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