linux-kernel - RE: [PATCH] lowmemorykiller: prevent multiple instances of low memory killer

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Message-ID: <D949F1A1ED65354FA281790D817657A4A4BF33CC84@seldmbx01.corpusers.net>
Date:	Mon, 15 Apr 2013 20:28:07 +0200
From:	"Dolkow, Snild" <Snild.Dolkow@...ymobile.com>
To:	"Anderö, Oskar" 
	<Oskar.Andero@...ymobile.com>,
	Dan Carpenter <dan.carpenter@...cle.com>
CC:	"devel@...verdev.osuosl.org" <devel@...verdev.osuosl.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Lekanovic, Radovan" <Radovan.Lekanovic@...ymobile.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Brian Swetland <swetland@...gle.com>
Subject: RE: [PATCH] lowmemorykiller: prevent multiple instances of low
 memory killer

>> > >From the comments in shrinker.h:
>> > "It should return the number of objects which remain in the cache.
>> > If it returns -1, it means it cannot do any scanning at this time
>> > (eg. there is a risk of deadlock). The callback must not return -1
>> > if nr_to_scan is zero."
>>
>
>IMO one should use the errno.h values - e.g. EBUSY might be a good value
>in this case. Does anyone know why the shrinker wants -1? Is there a
>reason?

The positive numbers are used to return information on the remaining cache size (again, see the comment I pasted above). We could use -EBUSY, but we'd have to change vmscan.c, which checks specifically for -1. I can't see a technical reason why -EBUSY couldn't have been chosen instead, but there's also no real reason to change it now.

//Snild
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