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SubjectRe: uart_startup: GFP_KERNEL allocation with IRQs disabled
On Fri, Aug 03, 2012 at 11:37:53AM +0200, Jiri Slaby wrote:
> On 08/03/2012 03:46 AM, Fengguang Wu wrote:
> > Hi all,
>
> Hi,
>
> > The IRQ should be disabled somewhere in the path walk, which makes
> > the GFP_KERNEL allocation in uart_startup() no longer valid..
> >
> > [ 0.499537] kworker/u:1 (29) used greatest stack depth: 7156 bytes left
> > [ 0.500947] ------------[ cut here ]------------
> > [ 0.501445] WARNING: at /c/kernel-tests/src/stable/kernel/lockdep.c:2739 lockdep_trace_alloc+0x86/0xb2()
> > [ 0.502413] Modules linked in:
> > [ 0.502766] Pid: 1, comm: init Not tainted 3.5.0-01258-g1ade992 #182
> > [ 0.503419] Call Trace:
> ...
> > [ 0.504381] [<c1079e7d>] get_zeroed_page+0xd/0xf
> > [ 0.504381] [<c10f976f>] uart_startup.part.8+0x46/0x152
> > [ 0.504381] [<c10f745f>] ? tty_port_tty_set+0x37/0x3c
> > [ 0.504381] [<c10fa175>] uart_open+0xc9/0x10b
> > [ 0.504381] [<c10fa0ac>] ? uart_suspend_port+0x229/0x229
> > [ 0.504381] [<c10f1bc2>] tty_open+0x26b/0x3d3
> > [ 0.504381] [<c109872a>] chrdev_open+0xf7/0x117
>
> This does not make sense to me. I would not blame TTY/serial for this.
> There is somebody who forgot to enable interrupts somewhere. Could you
> enable DEBUG_ATOMIC_SLEEP? It might trigger earlier revealing us the
> culprit.

Jiri, thanks for the info. After turning on DEBUG_ATOMIC_SLEEP, this
shows up which I just reported in another email. Ah I didn't notice
that it's running the same commit "x86: switch to generic sys_execve
and kernel_execve"..

[ 0.408108] BUG: sleeping function called from invalid context at /c/wfg/linux/kernel/rwsem.c:47
[ 0.408966] in_atomic(): 0, irqs_disabled(): 1, pid: 1, name: init
[ 0.409556] no locks held by init/1.
[ 0.409929] irq event stamp: 74784
[ 0.410247] hardirqs last enabled at (74783): [<c101e4e1>] do_page_fault+0x95/0x330
[ 0.411015] hardirqs last disabled at (74784): [<c1158337>] resume_userspace+0x17/0x28
[ 0.411759] softirqs last enabled at (74726): [<c102a42e>] __do_softirq+0x109/0x12d
[ 0.412011] softirqs last disabled at (74713): [<c10038f1>] do_softirq+0x5e/0xb3
[ 0.412011] Pid: 1, comm: init Not tainted 3.5.0-01258-g1ade992 #60
[ 0.412011] Call Trace:
[ 0.412011] [<c1025c95>] ? console_unlock+0x340/0x36d
[ 0.412011] [<c103fa89>] __might_sleep+0x159/0x161
[ 0.412011] [<c1156dc9>] down_write+0x17/0x40
[ 0.412011] [<c108c829>] sys_brk+0x21/0xe4
[ 0.412011] [<c115838d>] syscall_call+0x7/0xb

Thanks,
Fengguang


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