lkml.org 
[lkml]   [2009]   [Apr]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: 2.6.29 boot hang
    Rusty Russell wrote:
    > On Wednesday 01 April 2009 07:15:35 Randy Dunlap wrote:
    >> On a 4-proc x86_64 (HP BladeCenter, AMD CPUs) system, booting 2.6.29
    >> (or earlier, back to 2.6.28-6921-g873392c) hangs during boot.
    >>
    >> git bisect says:
    >> 873392ca514f87eae39f53b6944caf85b1a047cb is first bad commit
    >> commit 873392ca514f87eae39f53b6944caf85b1a047cb
    >> Author: Rusty Russell <rusty@rustcorp.com.au>
    >> Date: Wed Dec 31 23:54:56 2008 +1030
    >>
    >> PCI: work_on_cpu: use in drivers/pci/pci-driver.c
    >
    > ...
    >
    >> If I change CONFIG_MICROCODE_AMD=y to CONFIG_MICROCODE_AMD=n & rebuild,
    >> the kernel boots successfully.
    >
    > How very very odd. My first thought was a deadlock with keventd used
    > by work_on_cpu (changed in latest Linus tree), but the microcode code at
    > that version doesn't use work_on_cpu.

    Yep, I thought it a bit odd also.

    > So I don't think that's it, but this patch should canonically eliminate it:
    >
    > Subject: work_on_cpu(): rewrite it to create a kernel thread on demand
    > From: Andrew Morton <akpm@linux-foundation.org>

    This patch doesn't apply to 2.6.29-final, but it does apply to 2.6.29-git8,
    so I applied/tested it there. with surprising results (at least to me).

    2.6.29-git8 works for me without any patches applied. After applying
    this patch, I get the same boot hang that I was seeing with 2.6.29-final.

    Make sense to you??

    Thanks for your help.

    > The various implemetnations and proposed implemetnations of work_on_cpu()
    > are vulnerable to various deadlocks because they all used queues of some
    > form.
    >
    > Unrelated pieces of kernel code thus gained dependencies wherein if one
    > work_on_cpu() caller holds a lock which some other work_on_cpu() callback
    > also takes, the kernel could rarely deadlock.
    >
    > Fix this by creating a short-lived kernel thread for each work_on_cpu()
    > invokation.
    >
    > This is not terribly fast, but the only current caller of work_on_cpu() is
    > pci_call_probe().
    >
    > It would be nice to find some other way of doing the node-local
    > allocations in the PCI probe code so that we can zap work_on_cpu()
    > altogether. The code there is rather nasty. I can't think of anything
    > simple at this time...
    >
    > Cc: Rusty Russell <rusty@rustcorp.com.au>
    > Cc: Ingo Molnar <mingo@elte.hu>
    > Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    > Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
    > ---
    > kernel/workqueue.c | 36 +++++++++++++++++++-----------------
    > 1 file changed, 19 insertions(+), 17 deletions(-)
    >
    > diff -puN kernel/workqueue.c~work_on_cpu-rewrite-it-to-create-a-kernel-thread-on-demand kernel/workqueue.c
    > --- a/kernel/workqueue.c~work_on_cpu-rewrite-it-to-create-a-kernel-thread-on-demand
    > +++ a/kernel/workqueue.c
    > @@ -985,20 +985,20 @@ undo:
    > }
    >
    > #ifdef CONFIG_SMP
    > -static struct workqueue_struct *work_on_cpu_wq __read_mostly;
    >
    > struct work_for_cpu {
    > - struct work_struct work;
    > + struct completion completion;
    > long (*fn)(void *);
    > void *arg;
    > long ret;
    > };
    >
    > -static void do_work_for_cpu(struct work_struct *w)
    > +static int do_work_for_cpu(void *_wfc)
    > {
    > - struct work_for_cpu *wfc = container_of(w, struct work_for_cpu, work);
    > -
    > + struct work_for_cpu *wfc = _wfc;
    > wfc->ret = wfc->fn(wfc->arg);
    > + complete(&wfc->completion);
    > + return 0;
    > }
    >
    > /**
    > @@ -1009,17 +1009,23 @@ static void do_work_for_cpu(struct work_
    > *
    > * This will return the value @fn returns.
    > * It is up to the caller to ensure that the cpu doesn't go offline.
    > + * The caller must not hold any locks which would prevent @fn from completing.
    > */
    > long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg)
    > {
    > - struct work_for_cpu wfc;
    > -
    > - INIT_WORK(&wfc.work, do_work_for_cpu);
    > - wfc.fn = fn;
    > - wfc.arg = arg;
    > - queue_work_on(cpu, work_on_cpu_wq, &wfc.work);
    > - flush_work(&wfc.work);
    > -
    > + struct task_struct *sub_thread;
    > + struct work_for_cpu wfc = {
    > + .completion = COMPLETION_INITIALIZER_ONSTACK(wfc.completion),
    > + .fn = fn,
    > + .arg = arg,
    > + };
    > +
    > + sub_thread = kthread_create(do_work_for_cpu, &wfc, "work_for_cpu");
    > + if (IS_ERR(sub_thread))
    > + return PTR_ERR(sub_thread);
    > + kthread_bind(sub_thread, cpu);
    > + wake_up_process(sub_thread);
    > + wait_for_completion(&wfc.completion);
    > return wfc.ret;
    > }
    > EXPORT_SYMBOL_GPL(work_on_cpu);
    > @@ -1035,8 +1041,4 @@ void __init init_workqueues(void)
    > hotcpu_notifier(workqueue_cpu_callback, 0);
    > keventd_wq = create_workqueue("events");
    > BUG_ON(!keventd_wq);
    > -#ifdef CONFIG_SMP
    > - work_on_cpu_wq = create_workqueue("work_on_cpu");
    > - BUG_ON(!work_on_cpu_wq);
    > -#endif
    > }
    > _



    --
    ~Randy


    \
     
     \ /
      Last update: 2009-04-01 06:55    [W:0.029 / U:111.596 seconds]
    ©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site