Re: 2.6.7-mm7

From: Paul Mackerras (paulus_at_samba.org)
Date: 07/17/04

  • Next message: Paul Mackerras: "Re: [PATCH] 2.6 PPC64: EEH notifier call chain" 
    Date:	Sun, 18 Jul 2004 02:17:35 +1000
To: Andrew Morton <akpm@osdl.org>

    Andrew Morton writes:

    > hm, OK. It could be that the debug patch is a bit too aggressive, or that
    > ppc got lucky and happens to always be in state TASK_RUNNING when these
    > calls to schedule() occur.
    >
    > Maybe this task incorrectly has _TIF_NEED_RESCHED set?

    Is CONFIG_PREEMPT enabled?

    > Anyway, ppc guys: please take a look at the results from
    > ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.7/2.6.7-mm7/broken-out/detect-too-early-schedule-attempts.patch
    > and check that the kernel really should be calling schedule() at this time
    > and place, let us know?
    >
    > Thanks.
    >
    > > The first one looks like:
    > >
    > > Calibrating delay loop... 1064.96 BogoMIPS
    > > Mount-cache hash table entries: 512 (order: 0, 4096 bytes)
    > > Badness in schedule at kernel/sched.c:2153
    > > Call trace:
    > > [c00099e4] dump_stack+0x18/0x28
    > > [c0006bac] check_bug_trap+0x84/0xac
    > > [c0006d38] ProgramCheckException+0x164/0x1a4
    > > [c0006240] ret_from_except_full+0x0/0x4c
    > > [c02021bc] schedule+0x24/0x684
    > > [c0005e80] syscall_exit_work+0x108/0x10c
    > > [c02e0ad0] proc_root_init+0x14c/0x158
    > > [00000000] 0x0
    > > [c02ce5a0] start_kernel+0x158/0x184
    > > [000035fc] 0x35fc

    This looks like CONFIG_PREEMPT is enabled and _TIF_NEED_RESCHED is set
    at the end of handling a system call. AFAICS i386 will also call
    schedule in these circumstances. Does this mean we shouldn't do
    system calls until the scheduler is running?

    Paul.
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