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Re: kmemleak for MIPS

To: Daniel Baluta <daniel.baluta@gmail.com>
Subject: Re: kmemleak for MIPS
From: Catalin Marinas <catalin.marinas@arm.com>
Date: Wed, 30 Mar 2011 10:58:58 +0100
Cc: Maxin John <maxin.john@gmail.com>, naveen yadav <yad.naveen@gmail.com>, linux-mips@linux-mips.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Eric Dumazet <eric.dumazet@gmail.com>
In-reply-to: <AANLkTi=YB+nBG7BYuuU+rB9TC-BbWcJ6mVfkxq0iUype@mail.gmail.com>
Organization: ARM Limited
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References: <9bde694e1003020554p7c8ff3c2o4ae7cb5d501d1ab9@mail.gmail.com> <AANLkTinnqtXf5DE+qxkTyZ9p9Mb8dXai6UxWP2HaHY3D@mail.gmail.com> <1300960540.32158.13.camel@e102109-lin.cambridge.arm.com> <AANLkTim139fpJsMJFLiyUYvFgGMz-Ljgd_yDrks-tqhE@mail.gmail.com> <1301395206.583.53.camel@e102109-lin.cambridge.arm.com> <AANLkTim-4v5Cbp6+wHoXjgKXoS0axk1cgQ5AHF_zot80@mail.gmail.com> <1301399454.583.66.camel@e102109-lin.cambridge.arm.com> <AANLkTin0_gT0E3=oGyfMwk+1quqonYBExeN9a3=v=Lob@mail.gmail.com> <AANLkTi=gMP6jQuQFovfsOX=7p-SSnwXoVLO_DVEpV63h@mail.gmail.com> <1301476505.29074.47.camel@e102109-lin.cambridge.arm.com> <AANLkTi=YB+nBG7BYuuU+rB9TC-BbWcJ6mVfkxq0iUype@mail.gmail.com>
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On Wed, 2011-03-30 at 10:54 +0100, Daniel Baluta wrote:
> >> unreferenced object 0x8f90d000 (size 4096):
> >>   comm "swapper", pid 1, jiffies 4294937330 (age 815.000s)
> >>   hex dump (first 32 bytes):
> >>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> >>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
> >>   backtrace:
> >>     [<80529644>] alloc_large_system_hash+0x2f8/0x410
> >>     [<805383b4>] udp_table_init+0x4c/0x158
> >>     [<805384dc>] udp_init+0x1c/0x94
> >>     [<8053889c>] inet_init+0x184/0x2a0
> >>     [<80100584>] do_one_initcall+0x174/0x1e0
> >>     [<8051f348>] kernel_init+0xe4/0x174
> >>     [<80103d4c>] kernel_thread_helper+0x10/0x18
> >
> > If you for the kmemleak scan (via echo) a few times, do you get more
> > leaks? The udp_table_init() function looks like it could leak some
> > memory but I haven't seen it before. I'm not sure whether this is a
> > false positive or a real leak.
> 
> Looking again at udp_init_table it seem that a memory leak is possible.
> Could you post your .config and the full output of dmesg after booting.
> 
> A situation where CONFIG_BASE_SMALL is 0, and
> table->mask < UDP_HTABLE_SIZE_MIN - 1 would lead
> to a memory leak.

It's worth printing the table->mask on MIPS as well. I think have the
same configuration on ARM and put some printk's but the table->mask is
set to higher value and the second if condition is false. The checks
could be simply reordered but I don't know the reasoning behind the
current code sequence (I cc'ed Eric).

-- 
Catalin



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