Re: [BUG] Softlockup detected with linux-2.6.14-rt6

[john cooper <john.cooper@timesys.com>]

Luca Falavigna wrote:
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> I found this softlockup bug involving arts daemon using a
> linux-2.6.14-rt6 kernel (with "Complete Preemption" and "Detect Soft
> Lockups" compiled in).
> This bug does not happen everytime: I was able to reproduce it only
> three times in a week. Here is the oops message (obtained from my
> printer because system is frozen):
> 
> BUG: artsd:4177, possible softlockup detected on CPU#0!
> [<c0146db4>] softlockup_detected+0x34/0x40 (8)
> [<c0146e69>] softlockup_tick+0xa9/axb0 (20)
> [<c01388a1>] timer_interrupt+0x21/0x40 (12)
> [<c014724e>] handle_IRQ_event+0x63/0xf0 (12)
> [<c01476a3>] __do_IRQ+0xa3/0x150 (48)
> [<c0105594>] do_IRQ+0x34/0x70 (40)
> [<c0103d42>] common_interrupt+0x1a/0x20 (8)
> [<c0103d42>] common_interrupt+0x1a/0x20 (20)
> [<c01bfcc0>] __delay+0x20/0x30 (44)
> [<c91f16a4>] snd_timer_close+0x1b4/0x2b0 [snd_timer] (12)
> [<c0a7f36a>] fasync_helper+0x7a/0x100 (12)
> [<c91f307c>] snd_timer_user_release+0x4c/0x80 [snd_timer] (28)
> [<c016c14d>] __fput+0xad/0x1a0 (24)
> [<c0a6a632>] filp_close+0x52/0x90 (40)
> [<c016a6e0>] sys_close+0x70/0xc0 (24)
> [<c01032fd>] syscall_call+0x7/0xb (28)

We are seeing this too, particularly [IIRC exclusively]
on MIPS and PPC though there isn't any obvious target
architecture correlation.  It appears to be a false
positive as the system seems otherwise responsive to
general scheduling.  It's on my list to address but not
a priority just yet.

Adding a sched pri/policy printk to show_task() and
inserting a call to show_state() in the softlockup
detect routine should shed some light.

-john

-- 
john.cooper@timesys.com