Hi,
> 2010/10/22 B, Ravi <ravibabu@xxxxxx>:
> > Dear All,
> >
> > I am using Linux 2.6.33.7 stable kernel + patch-2.6.33.7-rt29 to test
> OHCI interface on TI OMAPL138 platform.
> > We observed that during bootup and OHCI init sequence the kernel hangs.
> If we use plane Linux 2.6.33.7 stable kernel
> > Without RT patch then OHCI works fine.
>
> Just a guess: Are you using the SLAB or SLOB allocator?
> We have seen that SLOB gives all kinds of weird problems in OHCI. SLAB
> works fine here.
I did further debugging on this and seems the issue could be due to
RT changes done at kernel/irq/manage.c
We faced the same hang issue even when CONFIG_PREEMPT_RT is disabled.
Then we tried below patch which reverts a change by RT patch and
observed it to start working fine.
------------ ------- ----------------
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -746,8 +746,9 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
rand_initialize_irq(irq);
}
- /* Preempt-RT setup for forced threading */
- preempt_hardirq_setup(new);
+ /* Oneshot interrupts are not allowed with shared */
+ if ((new->flags & IRQF_ONESHOT) && (new->flags & IRQF_SHARED))
+ return -EINVAL;
/*
* Check whether the interrupt nests into another interrupt
--------------------------------------
Unfortunately if we enable CONFIG_PREEMPT_RT with above patch applied,
Then we see a series of kernel panics as shown below.
--------------------------------------
(__bug+0x0/0x2c) from [<c0286c1c>] (rt_spin_lock_slowlock+0x88/0x24c)
(rt_spin_lock_slowlock+0x0/0x24c) from (rt_spin_lock+0x44/0x48)
rt_spin_lock+0x0/0x48) from [<c01cd4ec>] (ohci_irq+0x134/0x1c0)
(ohci_irq+0x0/0x1c0) from [<c01be3a0>] (usb_hcd_irq+0x3c/0x84)
(usb_hcd_irq+0x0/0x84) from [<c00693c4>] (handle_irq_action+0x9c/0xa0)
(handle_irq_action+0x0/0xa0) from [<c00693ec>] (handle_IRQ_event+0x24/0xd0)
handle_IRQ_event+0x0/0xd0) from [<c006b400>] (handle_edge_irq+0x15c/0x1d0)
(handle_edge_irq+0x0/0x1d0) from [<c0027074>] (asm_do_IRQ+0x74/0x94)
(asm_do_IRQ+0x0/0x94) from [<c0027b4c>] (__irq_svc+0x4c/0x9c)
---------------------------------------
There seems to be problem with kernel/irq/* changes done in RT patch.
Can some help me resolve this issue.
Regards,
Ajay
>
> Kind regards,
>
> Remy
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