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    SubjectRe: Commit 7eaceaccab5f40 causing boot hang.
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    On Mon, 2011-04-04 at 14:47 +0100, Richard Kennedy wrote:
    > On Thu, 2011-03-31 at 15:49 +0100, Richard Kennedy wrote:
    > > On Thu, 2011-03-31 at 15:33 +0200, Jens Axboe wrote:
    > >[...]
    > > > >>> Hi Jens,
    > > > >>>
    > > > >>> I'm seeing a problem with fio never completing when writing to 2 disks
    > > > >>> simultaneously. In my test case I'm writing 2Gb to both a LVM volume & a
    > > > >>> pata drive on x86_64 on a AMD X2. Could this be a related issue?
    > > > >>>
    > > > >>> I'm not getting anything reported in the log, lockup detection doesn't
    > > > >>> report anything either. The write seems to have finished (the disk light
    > > > >>> activity has stopped) and the cpu cores are both below 10% usage, but
    > > > >>> fio never returns. The test does complete some times, but it seems to be
    > > > >>> one 1 in 4.
    > > > >>
    > > > >> So when you say PATA, it's /dev/hdaX something as well?
    > > > >>
    > > > >>> I'm going to try tracing it and see if I can spot where it's stuck.
    > > > >>
    > > > >> Thanks, that would be nice.
    > > > >>
    > > > > The second drive is /dev/sdb1 mounted on /opt, both file systems are
    > > > > ext4.
    > > >
    > > > So probably not related. What does the fio job look like?
    > > >
    > > fio job file --
    > > [global]
    > > pre_read=1
    > > ioengine=mmap
    > >
    > > [f1]
    > > size=2g
    > > rw=write
    > > directory=/home/tests
    > >
    > > [f2]
    > > size=2g
    > > rw=write
    > > directory=/opt/tests
    > >
    > > Fio gets run from a script that also collects stats but it's been
    > > running without any problems up until 2.6.39-rc1.
    > >
    > Hi Jens
    > I've upgrade to the latest fio version in the git repo 1.51 and I'm
    > still seeing this problem.
    >
    > Fio gets stuck after it writes the 100% complete message and strace on
    > the processes shows this.
    >
    > the controlling fio process :-
    > ...
    > [pid 8439] wait4(8442, 0x7fff848203ac, WNOHANG, NULL) = 0
    > [pid 8439] nanosleep({0, 10000000}, NULL) = 0
    > [pid 8439] wait4(8441, 0x7fff848203ac, WNOHANG, NULL) = 0
    > [pid 8439] wait4(8442, 0x7fff848203ac, WNOHANG, NULL) = 0
    > [pid 8439] nanosleep({0, 10000000}
    >
    > & the 2 workers are both stopped here, strace shows only the one line
    > for each process.
    >
    > Process 8441 attached - interrupt to quit
    > futex(0x7f9db76a802c, FUTEX_WAIT_PRIVATE, 2, NULL
    >
    >
    > Process 8442 attached - interrupt to quit
    > futex(0x7f9db76a802c, FUTEX_WAIT_PRIVATE, 2, NULL
    >
    > How do I find out which futex it's waiting for?
    > Any ideas where I should look next ?
    >
    > I can run the same test successfully on 2.6.38 so is it worth trying to
    > bisect this ?
    >
    > thanks
    > Richard
    >
    My problem has gone away in v2.6.39-rc3.
    I've just finished bisecting it down to 6de9843dab3f, & that got
    reverted in rc3, so no problem ;)

    (The data corruption caused by that faulty commit was zeroing out the
    shared mutexs in fio & the worker threads were getting stuck on the
    writeout_mutex.)

    regards
    Richard






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