Messages in this thread | | | Date | Tue, 25 Aug 2009 10:32:22 +0200 | From | Ingo Molnar <> | Subject | Re: WARNING: kmemcheck: Caught 32-bit read from uninitialized memory (f6f6e1a4), by kmemleak's scan_block() |
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* Vegard Nossum <vegard.nossum@gmail.com> wrote:
> 2009/8/25 Ingo Molnar <mingo@elte.hu>: > > > > FYI, -tip testing triggered the following kmemcheck warning in > > kmemleak: > > > > PM: Adding info for No Bus:vcsa7 > > WARNING: kmemcheck: Caught 32-bit read from uninitialized memory (f6f6e1a4) > > d873f9f600000000c42ae4c1005c87f70000000070665f666978656400000000 > > ??i i i i u u u u i i i i i i i i i i i i i i i i i i i i i u u u > > ?? ?? ?? ?? ^ > > > > Pid: 3091, comm: kmemleak Not tainted (2.6.31-rc7-tip #1303) P4DC6 > > EIP: 0060:[<c110301f>] EFLAGS: 00010006 CPU: 0 > > EIP is at scan_block+0x3f/0xe0 > > EAX: f40bd700 EBX: f40bd780 ECX: f16b46c0 EDX: 00000001 > > ESI: f6f6e1a4 EDI: 00000000 EBP: f10f3f4c ESP: c2605fcc > > ??DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068 > > CR0: 8005003b CR2: e89a4844 CR3: 30ff1000 CR4: 000006f0 > > DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000 > > DR6: ffff4ff0 DR7: 00000400 > > ??[<c110313c>] scan_object+0x7c/0xf0 > > ??[<c1103389>] kmemleak_scan+0x1d9/0x400 > > ??[<c1103a3c>] kmemleak_scan_thread+0x4c/0xb0 > > ??[<c10819d4>] kthread+0x74/0x80 > > ??[<c10257db>] kernel_thread_helper+0x7/0x3c > > ??[<ffffffff>] 0xffffffff > > kmemleak: 515 new suspected memory leaks (see /sys/kernel/debug/kmemleak) > > kmemleak: 42 new suspected memory leaks (see /sys/kernel/debug/kmemleak) > > > > config attached. (And this is the first documented case of a kmem > > civil war i guess ;-) > > Already the patch to make kmemcheck and kmemleak mutually > exclusive is underway. It is not surprising that kmemleak is > scanning uninitialized memory. But if you say that you have tried > it before, it is strange that it didn't appear until now.
i had kmemleak off for long periods of time in -tip, it stabilized recently:
earth4:~/tip> gll linus..out-of-tree | grep kmeml d4ece0f: Revert "Revert "Revert "Revert "Revert "kmemleak: Disable it for now""""" 3aa8916: kmemleak: Ignore the aperture memory hole on x86_64 0f97c9f: Revert "kmemleak: Ignore the aperture memory hole on x86_64" eedff6e: Revert "Revert "Revert "Revert "kmemleak: Disable it for now"""" a1bf608: kmemleak: Ignore the aperture memory hole on x86_64 74a9357: kmemleak: Allow rescheduling during an object scanning a047bfe: Revert "kmemleak: Allow rescheduling during an object scanning" 47dc143: Revert "Revert "Revert "kmemleak: Disable it for now""" 4a3f3f7: Revert "Revert "kmemleak: Disable it for now"" 39ac9ee: kmemleak: Allow rescheduling during an object scanning 085fac5: Revert "kmemleak: Disable it for now" da0ce63: kmemleak: Disable it for now f6a5295: kmemleak: Mark nice +10 5ba1a81: kmemleak: Fix scheduling-while-atomic bug
plus not all of my systems have kmemcheck testing enabled. These two factors would explain the latency of it i think.
> In any case, I don't think it is very productive to run them both > at the same time, simply because kmemcheck slows every memory > access down so much and scanning memory doesn't exactly help that. > It _could_ be useful to have them compiled into the same kernel, > though, e.g. a distro "-debug" kernel. > > Maybe you can just add the "depends on !KMEMLEAK" to > CONFIG_KMEMCHECK in tip/out-of-tree for now?
i think it would be far more intelligent to annotate those accesses by kmemleak as 'trust me, dont check'. Willing to test such a patch.
Ingo
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