Messages in this thread | | | Date | Tue, 22 May 2012 10:47:57 +0100 | From | Catalin Marinas <> | Subject | Re: [PATCH] sysctl: Suppress kmemleak messages |
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On Tue, May 22, 2012 at 02:04:17AM +0100, Steven Rostedt wrote: > Not sure who the owner is of kernel/sysctl.c, so I'm just sending this > patch to you :-) > > The register_sysctl_table() is a strange function, as it makes internal > allocations (a header) to register a sysctl_table. This header is a > handle to the table that is created, and can be used to unregister the > table. But if the table is permanent and never unregistered, the header > acts the same as a static variable. > > Unfortunately, this allocation of memory that is never expected to be > freed, fools kmemleak in thinking that we have leaked memory. For those > sysctl tables that are never unregistered, and have no pointer > referencing them, kmemleak will think that these are memory leaks: > > unreferenced object 0xffff880079fb9d40 (size 192): > comm "swapper/0", pid 0, jiffies 4294667316 (age 12614.152s) > 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: > [<ffffffff8146b590>] kmemleak_alloc+0x73/0x98 > [<ffffffff8110a935>] kmemleak_alloc_recursive.constprop.42+0x16/0x18 > [<ffffffff8110b852>] __kmalloc+0x107/0x153 > [<ffffffff8116fa72>] kzalloc.constprop.8+0xe/0x10 > [<ffffffff811703c9>] __register_sysctl_paths+0xe1/0x160 > [<ffffffff81170463>] register_sysctl_paths+0x1b/0x1d > [<ffffffff8117047d>] register_sysctl_table+0x18/0x1a > [<ffffffff81afb0a1>] sysctl_init+0x10/0x14 > [<ffffffff81b05a6f>] proc_sys_init+0x2f/0x31 > [<ffffffff81b0584c>] proc_root_init+0xa5/0xa7 > [<ffffffff81ae5b7e>] start_kernel+0x3d0/0x40a > [<ffffffff81ae52a7>] x86_64_start_reservations+0xae/0xb2 > [<ffffffff81ae53ad>] x86_64_start_kernel+0x102/0x111 > [<ffffffffffffffff>] 0xffffffffffffffff > > > The sysctl_base_table used by sysctl itself is one such instance that > registers the table to never be unregistered. > > Use kmemleak_not_leak() to suppress the kmemleak false positive. > > [ applied against 3.4 ] > > Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
FWIW,
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
(for the use of the kmemleak API :))
-- Catalin
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