On Fri, 2011-12-02 at 15:08 -0800, Frank Rowand wrote:
> Hi Steve,
>
> I get a "sleeping function called from invalid context" when I invoke sysrq Z.
>
> I get this both with CONFIG_MAGIC_SYSRQ_FORCE_PRINTK enabled and disabled.
Patient: Hey doctor, it hurts when I do this
Doctor: Don't do that.
>
> 3.0.12-rt29
> ARM Pandaboard
>
> I have not tried this on 3.2-rc4-rt5.
>
> [ 900.963226] SysRq : Dump ftrace buffer
> [ 900.967163] Dumping ftrace buffer:
> [ 900.970733] BUG: sleeping function called from invalid context at kernel/rtmutex.c:645
> [ 900.985137] in_atomic(): 0, irqs_disabled(): 128, pid: 563, name: irq/106-OMAP UA
> [ 900.992980] 2 locks held by irq/106-OMAP UA/563:
> [ 900.997833] #0: (&port_lock_key){+.+...}, at: [<c02d8b14>] serial_omap_irq+0x4c/0x7dc
> [ 901.006286] #1: (sysrq_key_table_lock){+.+...}, at: [<c02c13a0>] __handle_sysrq+0x20/0x18c
> [ 901.015167] irq event stamp: 45345
> [ 901.018737] hardirqs last enabled at (45344): [<c0482f68>] _raw_spin_unlock_irq+0x24/0x4c
> [ 901.027435] hardirqs last disabled at (45345): [<c00fb854>] ftrace_dump+0x14/0x23c
> [ 901.035400] softirqs last enabled at (0): [<c009dca8>] copy_process+0x364/0xf84
> [ 901.043182] softirqs last disabled at (0): [< (null)>] (null)
> [ 901.049499] [<c00681b8>] (unwind_backtrace+0x0/0xf0) from [<c04824d0>] (rt_spin_lock+0x24/0x5c)
> [ 901.058654] [<c04824d0>] (rt_spin_lock+0x24/0x5c) from [<c00f3b34>] (read_buffer_lock+0x4c/0x6c)
> [ 901.067871] [<c00f3b34>] (read_buffer_lock+0x4c/0x6c) from [<c00f5908>] (ring_buffer_empty_cpu+0x50/0x7c)
Grumble. I really don't want to make the read_buffer_lock a real spin
lock. I'll have to see what else is called when its held. I you could
try to make it into a raw_spin_lock() if you want and see if it causes
any more issues.
I guess the other question is, what disabled interrupts?
Oh, it's in the lockdep splat above :-p
It's the ftrace_dump code that disables interrupts.
Oh! looking into the ring_buffer code, could you add this:
(totally untested)
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 2467714..2ffbb9d 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -1045,7 +1045,7 @@ static inline int ok_to_lock(void)
if (in_nmi())
return 0;
#ifdef CONFIG_PREEMPT_RT_FULL
- if (in_atomic())
+ if (in_atomic() || irqs_disabled())
return 0;
#endif
return 1;
> [ 901.077911] [<c00f5908>] (ring_buffer_empty_cpu+0x50/0x7c) from [<c00fa3cc>] (trace_empty+0x58/0xd8)
> [ 901.087524] [<c00fa3cc>] (trace_empty+0x58/0xd8) from [<c00fb9f8>] (ftrace_dump+0x1b8/0x23c)
> [ 901.096374] [<c00fb9f8>] (ftrace_dump+0x1b8/0x23c) from [<c02c1428>] (__handle_sysrq+0xa8/0x18c)
> [ 901.105621] [<c02c1428>] (__handle_sysrq+0xa8/0x18c) from [<c02d90cc>] (serial_omap_irq+0x604/0x7dc)
> [ 901.115203] [<c02d90cc>] (serial_omap_irq+0x604/0x7dc) from [<c00eb934>] (irq_forced_thread_fn+0x20/0x40)
> [ 901.125244] [<c00eb934>] (irq_forced_thread_fn+0x20/0x40) from [<c00eb7dc>] (irq_thread+0x144/0x1e4)
> [ 901.134887] [<c00eb7dc>] (irq_thread+0x144/0x1e4) from [<c00c094c>] (kthread+0x7c/0x84)
> [ 901.143310] [<c00c094c>] (kthread+0x7c/0x84) from [<c0061e30>] (kernel_thread_exit+0x0/0x8)
> [ 901.152496] (ftrace buffer empty)
>
> -Frank
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