Re: idr_remove

From: Lorenzo Hernández García-Hierro (lorenzo_at_gnu.org)
Date: 02/22/05

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    To: russell@coker.com.au
Date:	Tue, 22 Feb 2005 18:35:40 +0100

    El sáb, 19-02-2005 a las 23:32 +1100, Russell Coker escribió:
    > http://marc.theaimsgroup.com/?l=linux-kernel&m=109838483518162&w=2
    >
    > I am getting messages "idr_remove called for id=0 which is not allocated" when
    > SE Linux denies search access to /dev/pts.
    >
    > The attached file has some klogd output showing the situation, triggered in
    > this case by installing a new kernel package on a SE Debian system. The
    > above URL references Jim Houston's message with the patch to add this
    > warning.

    The problem seems to be in a call back from idr_remove() to
    sub_remove()@/lib/idr.c:284 which leads to calling idr_remove_warning(),
    doing the weird stack dump, when some logics don't work as expected.

    Jan 17 13:45:43 lyta kernel: [dump_stack+23/32] dump_stack+0x17/0x20
    Jan 17 13:45:43 lyta kernel: [sub_remove+233/240] sub_remove+0xe9/0xf0
    Jan 17 13:45:43 lyta kernel: [idr_remove+35/144] idr_remove+0x23/0x90

    The spurious function called by sub_remove() (leads to the
    dump_stack+0x17/0x20):

    +static void idr_remove_warning(int id)
    +{
    + printk("idr_remove called for id=%d which is not allocated.\n", id);
    + dump_stack();
    +}
    +

    The changes that lead to such warning and stack dump

    @sub_remove
    + n = id & IDR_MASK;
    + if (likely(p != NULL && test_bit(n, &p->bitmap))){
    (...etc...)

    idr_remove() is called, among other places, within the Device Mapper
    (DM) code that I suppose you are using, right?

    I don't have time to make further checking, but seems to be somewhat
    type of devices handling and IDR minor numbers allocation tracking
    black magic, someone could have a further a look at it?

    Cheers, 

    -- 
Lorenzo Hernández García-Hierro <lorenzo@gnu.org> 
[1024D/6F2B2DEC] & [2048g/9AE91A22][http://tuxedo-es.org]

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