Le lundi 26 septembre 2011 à 23:17 +0800, Huajun Li a écrit :
> Memory leak detector gives following memory leak report, it seems the
> report is triggered by net/core/flow.c, but actually, it should be a
> false positive report.
> So, is there any idea from kmemleak side to fix/disable this false
> positive report like this?
> Yes, kmemleak_not_leak(...) could disable it, but is it suitable for this case ?
>
> BTW, I wrote a simple test code to emulate net/core/flow.c behavior at
> this stage which triggers the report, and it could also make kmemleak
> give similar report, please check below test code:
>
> kernel version:
> #uname -a
> Linux 3.1.0-rc7 #22 SMP Tue Sep 26 05:43:01 CST 2011 x86_64 x86_64
> x86_64 GNU/Linux
>
> memory leak report:
> -------------------------------------------------------------------------------------------
> unreferenced object 0xffff880073a70000 (size 8192):
> comm "swapper", pid 1, jiffies 4294937832 (age 445.740s)
> 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:
> [<ffffffff8124db64>] create_object+0x144/0x360
> [<ffffffff8191192e>] kmemleak_alloc+0x7e/0x110
> [<ffffffff81235b26>] __kmalloc_node+0x156/0x3a0
> [<ffffffff81935512>] flow_cache_cpu_prepare.clone.1+0x58/0xc0
> [<ffffffff8214c361>] flow_cache_init_global+0xb6/0x1af
> [<ffffffff8100225d>] do_one_initcall+0x4d/0x260
> [<ffffffff820ec2e9>] kernel_init+0x161/0x23a
> [<ffffffff8194ab04>] kernel_thread_helper+0x4/0x10
> [<ffffffffffffffff>] 0xffffffffffffffff
> unreferenced object 0xffff880073a74290 (size 8192):
> comm "swapper", pid 1, jiffies 4294937832 (age 445.740s)
> 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:
> [<ffffffff8124db64>] create_object+0x144/0x360
> [<ffffffff8191192e>] kmemleak_alloc+0x7e/0x110
> [<ffffffff81235b26>] __kmalloc_node+0x156/0x3a0
> [<ffffffff81935512>] flow_cache_cpu_prepare.clone.1+0x58/0xc0
> [<ffffffff8214c361>] flow_cache_init_global+0xb6/0x1af
> [<ffffffff8100225d>] do_one_initcall+0x4d/0x260
> [<ffffffff820ec2e9>] kernel_init+0x161/0x23a
> [<ffffffff8194ab04>] kernel_thread_helper+0x4/0x10
> [<ffffffffffffffff>] 0xffffffffffffffff
>
>
>
> Simple test code to reproduce a similar report:
> -----------------------------------------------------------------------------------------
> MODULE_LICENSE("GPL");
>
> struct test {
> int *pt;
char spaceholder[30000];
> };
>
> static struct test __percpu *percpu;
>
> static int __init test_init(void)
> {
> int i;
>
> percpu = alloc_percpu(struct test);
> if (!percpu)
> return -ENOMEM;
>
> for_each_online_cpu(i) {
> struct test *p = per_cpu_ptr(percpu, i);
> p->pt = kmalloc(sizeof(int), GFP_KERNEL);
> }
>
> return 0;
> }
>
> static void __exit test_exit(void)
> {
> int i;
>
> for_each_possible_cpu(i) {
> struct test *p = per_cpu_ptr(percpu, i);
> if (p->pt)
> kfree(p->pt);
> }
>
> if (percpu)
> free_percpu(percpu);
> }
> module_init(test_init);
> module_exit(test_exit);
CC lkml and percpu maintainers (Tejun Heo & Christoph Lameter ) as well
AFAIK this false positive only occurs if percpu data is allocated
outside of embedded pcu space.
(grep pcpu_get_vm_areas /proc/vmallocinfo)
I suspect this is a percpu/kmemleak cooperation problem (a missing
kmemleak_alloc() ?)
I am pretty sure kmemleak_not_leak() is not the right answer to this
problem.
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