Re: [PATCH] rt: x86: extend signal send delay to 32 bit

[Shi, Yang]

On 12/11/2015 10:05 AM, Sebastian Andrzej Siewior wrote:
> * Yang Shi | 2015-12-10 10:58:51 [-0800]:
>
> > When running some ptrace single step tests on x86-32 machine, the below problem
> > is triggered:
> >
> > BUG: sleeping function called from invalid context at linux-rt/kernel/locking/rtmutex.c:917
> > in_atomic(): 1, irqs_disabled(): 0, pid: 1041, name: dummy2
> > INFO: lockdep is turned off.
> > Preemption disabled at:[<c100326f>] do_debug+0x1f/0x1a0
> >
> > CPU: 10 PID: 1041 Comm: dummy2 Tainted: G        W       4.1.13-rt13 #1
> > Hardware name: Intel Corporation S5520HC/S5520HC, BIOS S5500.86B.01.10.0025.030220091519 03/02/2009
> > 00000000 00000000 e1811e80 c1aa8306 00000000 e1811ea8 c1080517 c1d8b2e8
> > c100326f c100326f 00000411 e5b7d5b4 e1d521c4 00000005 e1811f74 e1811ec4
> > c1ab0eff e1d51cc0 e5b7d180 c1081403 e5b7d180 e5b7d180 e1811ee4 c1064b5a
> > Call Trace:
> > [<c1aa8306>] dump_stack+0x46/0x5c
> > [<c1080517>] ___might_sleep+0x137/0x220
> > [<c100326f>] ? do_debug+0x1f/0x1a0
> > [<c100326f>] ? do_debug+0x1f/0x1a0
> > [<c1ab0eff>] rt_spin_lock+0x1f/0x80
> > [<c1081403>] ? preempt_count_sub+0xb3/0x110
> > [<c1064b5a>] do_force_sig_info+0x2a/0xc0
> > [<c106567d>] force_sig_info+0xd/0x10
> > [<c1010cff>] send_sigtrap+0x6f/0x80
> > [<c10033b1>] do_debug+0x161/0x1a0
> > [<c1ab2921>] debug_stack_correct+0x2e/0x35
> >
> > Signal send delay is just available for x86-64, x86-32 needs it too.
>
> This is new, this was not the case earlier. New means since v4.0-rc1 which

Yes, it is. We didn't find this problem in earlier version kernel (I'd 
say 3.x).

> is when 959274753857 ("x86, traps: Track entry into and exit from IST
> context") got merged.
> Since now ist_enter() disables preemption in any case, our hacks to
> conditional_sti_ist() are pointless and could be removed.

I'm supposed you will revert it and not need a revert patch from me.

Thanks for the deeper cause analysis.

Yang

> Sebastian

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