Messages in this thread Patch in this message | | | From | Marc Dietrich <> | Subject | Re: [NFS] 2.6.23-rc1-mm2 | Date | Mon, 6 Aug 2007 13:05:23 +0200 |
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Hi,
Am Monday 06 August 2007 08:24 schrieb Johannes Berg: > On Fri, 2007-08-03 at 21:21 +0400, Oleg Nesterov wrote: > > To avoid a possible confusion: it is still OK if work->func() flushes > > its own workqueue, so strictly speaking this trace is false positive, > > but it would be very nice if we can get rid of this practice. > > I just had a thought: we could get rid of this warning by using a > read-lock here. That way, flushing from within a work function (which > would be seen as read-after-read recursive lock) won't trigger this > warning. Patch below. This would, however, also get rid of any warnings > for run_workqueue recursion. Which again we may or may not want, the > code inidicates that it should be allowed up to a depth of three. > > However, the question whether we should allow flush_workqueue from > within a struct work is mainly an API policy issue; it doesn't hurt to > flush a workqueue from within a work, but it is probably nearer the > intent to use targeted cancel_work_sync() or such. OTOH, one could > imagine situations where multiple different work structs are on that > workqueue belonging to the same subsystem and then the general > flush_scheduled_work() call is the only way to guarantee nothing is on > scheduled at a given point... I don't feel qualified to make the > decision for or against allowing this use of the API at this point. > > Marc, do you have an easy way to trigger this warning? Could you verify > that it goes away with the patch below applied?
just booting into X is enough.
I applied the patch, but now I get:
================================= [ INFO: inconsistent lock state ] 2.6.23-rc1-mm2 #4 --------------------------------- inconsistent {softirq-on-W} -> {in-softirq-W} usage. swapper/0 [HC0[0]:SC1[1]:HE1:SE0] takes: (rpc_credcache_lock){-+..}, at: [<c01dc487>] _atomic_dec_and_lock+0x17/0x60 {softirq-on-W} state was registered at: [<c013e870>] __lock_acquire+0x650/0x1030 [<c013f2b1>] lock_acquire+0x61/0x80 [<c02db9ac>] _spin_lock+0x2c/0x40 [<c01dc487>] _atomic_dec_and_lock+0x17/0x60 [<dced55fd>] put_rpccred+0x5d/0x100 [sunrpc] [<dced56c1>] rpcauth_unbindcred+0x21/0x60 [sunrpc] [<dced3fd4>] a0 [sunrpc] [<dcecefe0>] rpc_call_sync+0x30/0x40 [sunrpc] [<dcedc73b>] rpcb_register+0xdb/0x180 [sunrpc] [<dced65b3>] svc_register+0x93/0x160 [sunrpc] [<dced6ebe>] __svc_create+0x1ee/0x220 [sunrpc] [<dced7053>] svc_create+0x13/0x20 [sunrpc] [<dcf6d722>] nfs_callback_up+0x82/0x120 [nfs] [<dcf48f36>] nfs_get_client+0x176/0x390 [nfs] [<dcf49181>] nfs4_set_client+0x31/0x190 [nfs] [<dcf49983>] nfs4_create_server+0x63/0x3b0 [nfs] [<dcf52426>] nfs4_get_sb+0x346/0x5b0 [nfs] [<c017b444>] vfs_kern_mount+0x94/0x110 [<c0190a62>] do_mount+0x1f2/0x7d0 [<c01910a6>] sys_mount+0x66/0xa0 [<c0104046>] syscall_call+0x7/0xb [<ffffffff>] 0xffffffff irq event stamp: 5277830 hardirqs last enabled at (5277830): [<c017530a>] kmem_cache_free+0x8a/0xc0 hardirqs last disabled at (5277829): [<c01752d2>] kmem_cache_free+0x52/0xc0 softirqs last enabled at (5277798): [<c0124173>] __do_softirq+0xa3/0xc0 softirqs last disabled at (5277817): [<c01241d7>] do_softirq+0x47/0x50
other info that might help us debug this: no locks held by swapper/0.
stack backtrace: [<c0104fda>] show_trace_log_lvl+0x1a/0x30 [<c0105c02>] show_trace+0x12/0x20 [<c0105d15>] dump_stack+0x15/0x20 [<c013ccc3>] print_usage_bug+0x153/0x160 [<c013d8b9>] mark_lock+0x449/0x620 [<c013e824>] __lock_acquire+0x604/0x1030 [<c013f2b1>] lock_acquire+0x61/0x80 [<c02db9ac>] _spin_lock+0x2c/0x40 [<c01dc487>] _atomic_dec_and_lock+0x17/0x60 [<dced55fd>] put_rpccred+0x5d/0x100 [sunrpc] [<dcf6bf83>] nfs_free_delegation_callback+0x13/0x20 [nfs] [<c012f9ea>] __rcu_process_callbacks+0x6a/0x1c0 [<c012fb52>] rcu_process_callbacks+0x12/0x30 [<c0124218>] tasklet_action+0x38/0x80 [<c0124125>] __do_softirq+0x55/0xc0 [<c01241d7>] do_softirq+0x47/0x50 [<c0124605>] irq_exit+0x35/0x40 [<c0112463>] smp_apic_timer_interrupt+0x43/0x80 [<c0104a77>] apic_timer_interrupt+0x33/0x38 [<c02690df>] cpuidle_idle_call+0x6f/0x90 [<c01023c3>] cpu_idle+0x43/0x70 [<c02d8c27>] rest_init+0x47/0x50 [<c03bcb6a>] start_kernel+0x22a/0x2b0 [<00000000>] 0x0 =======================
also, sometimes this kernel hangs because of nfs accessing processes remain in D state.
Marc
> johannes > > --- > kernel/workqueue.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > --- wireless-dev.orig/kernel/workqueue.c 2007-08-06 08:11:23.297846657 > +0200 +++ wireless-dev/kernel/workqueue.c 2007-08-06 08:19:54.727846657 > +0200 @@ -272,7 +272,7 @@ static void run_workqueue(struct cpu_wor > > BUG_ON(get_wq_data(work) != cwq); > work_clear_pending(work); > - lock_acquire(&cwq->wq->lockdep_map, 0, 0, 0, 2, _THIS_IP_); > + lock_acquire(&cwq->wq->lockdep_map, 0, 0, 1, 2, _THIS_IP_); > lock_acquire(&lockdep_map, 0, 0, 0, 2, _THIS_IP_); > f(work); > lock_release(&lockdep_map, 1, _THIS_IP_); > @@ -395,7 +395,7 @@ void fastcall flush_workqueue(struct wor > int cpu; > > might_sleep(); > - lock_acquire(&wq->lockdep_map, 0, 0, 0, 2, _THIS_IP_); > + lock_acquire(&wq->lockdep_map, 0, 0, 1, 2, _THIS_IP_); > lock_release(&wq->lockdep_map, 1, _THIS_IP_); > for_each_cpu_mask(cpu, *cpu_map) > flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu)); > @@ -779,7 +779,7 @@ static void cleanup_workqueue_thread(str > if (cwq->thread == NULL) > return; > > - lock_acquire(&cwq->wq->lockdep_map, 0, 0, 0, 2, _THIS_IP_); > + lock_acquire(&cwq->wq->lockdep_map, 0, 0, 1, 2, _THIS_IP_); > lock_release(&cwq->wq->lockdep_map, 1, _THIS_IP_); > > flush_cpu_workqueue(cwq);
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