Messages in this thread | | | Date | Thu, 1 Apr 2010 12:33:05 -0500 | From | "Serge E. Hallyn" <> | Subject | Re: [2.6.31 and later] "struct pid" leak. |
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Quoting Serge E. Hallyn (serue@us.ibm.com): > Quoting Oleg Nesterov (oleg@redhat.com): > > On 03/31, Andrew Morton wrote: > > > > > > On Tue, 30 Mar 2010 16:31:13 +0100 > > > Catalin Marinas <catalin.marinas@arm.com> wrote: > > > > > > > Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> wrote: > > > > > I got below report with 2.6.33.1 . > > > > > > > > > > unreferenced object 0xde144600 (size 64): > > > > > comm "init", pid 1, jiffies 4294678101 (age 291.508s) > > > > > hex dump (first 32 bytes): > > > > > 02 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > > > > > 00 00 00 00 04 76 ae de d1 76 43 c0 d6 08 00 00 .....v...vC..... > > > > > backtrace: > > > > > [<c0481704>] create_object+0x121/0x1ef > > > > > [<c05f546b>] kmemleak_alloc+0x25/0x42 > > > > > [<c047e326>] kmemleak_alloc_recursive+0x1c/0x22 > > > > > [<c047e36e>] kmem_cache_alloc+0x42/0x68 > > > > > [<c0437701>] alloc_pid+0x19/0x288 > > > > > [<c0428acc>] copy_process+0x95a/0xdac > > > > > [<c04290d8>] do_fork+0x129/0x261 > > > > > [<c0407de5>] sys_clone+0x1f/0x24 > > > > > [<c040292d>] ptregs_clone+0x15/0x28 > > > > > [<ffffffff>] 0xffffffff > > > > > unreferenced object 0xdfa96a40 (size 64): > > > > > comm "login", pid 2259, jiffies 4294719437 (age 250.179s) > > > > > hex dump (first 32 bytes): > > > > > 02 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ > > > > > 00 00 00 00 60 39 ae de d1 76 43 c0 bb 09 00 00 ....`9...vC..... > > > > > backtrace: > > > > > [<c0481704>] create_object+0x121/0x1ef > > > > > [<c05f546b>] kmemleak_alloc+0x25/0x42 > > > > > [<c047e326>] kmemleak_alloc_recursive+0x1c/0x22 > > > > > [<c047e36e>] kmem_cache_alloc+0x42/0x68 > > > > > [<c0437701>] alloc_pid+0x19/0x288 > > > > > [<c0428acc>] copy_process+0x95a/0xdac > > > > > [<c04290d8>] do_fork+0x129/0x261 > > > > > [<c0407de5>] sys_clone+0x1f/0x24 > > > > > [<c040292d>] ptregs_clone+0x15/0x28 > > > > > [<ffffffff>] 0xffffffff > > > > > > > > I reported similar leaks last year - > > > > http://lkml.org/lkml/2009/7/8/422. There is some analysis in the thread > > > > above of the reference counting but I couldn't figure out where it goes > > > > wrong. It looks to me like there isn't any reference to a struct pid > > > > block but its reference count is 2. > > > > > > > > There is a bugzilla entry as well - > > > > https://bugzilla.kernel.org/show_bug.cgi?id=13868 > > > > > > > > > > Let's bug some people by cc'ing them ;) > > > > Oh. It is hardly possibly to find the unbalanced get_pid() via grep. > > > > IIRC, I sent the debugging patch which tracks get/put pid, but I can't > > recall if anybody tried this patch. Hmm, and I can't find that patch > > or the previous discussion in my maildir... > > > > Catalin, Tetsuo, any chance you can remind me if this patch was used? > > > > Oleg. > > [ probably sounding like a moron, but... ] > > Looking through vt_ioctl.c, I get the feeling that the ttys will > hang onto vc->vt_pid until either getting a SAK or until someone > new logs in. I don't see where logging out will cause a reset_vc(). > So when the logged in task logs out, does vt_pid keep a ref to the > pid which now no longer exists? > > Came to mind bc I notice that every trace you've sent has included > /bin/login or X... > > -serge
In particular, if vt_ioctl is called with VT_RELDISP, then complete_change_console() will get called, which will kill vc->vt_pid, but it will only call reset_vc(vc) if that kill_pid failed. reset_vc() is needed to do our last put_pid().
I could be way off base here, but...
-serge
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