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Subject: Re: [PATCH 1/2] ARC: show_regs: avoid page allocator
To:     Eugeniy Paltsev <eugeniy.paltsev@synopsys.com>,
        "vineet.gupta1@synopsys.com" <vineet.gupta1@synopsys.com>,
        "linux-snps-arc@lists.infradead.org" 
        <linux-snps-arc@lists.infradead.org>
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        "peterz@infradead.org" <peterz@infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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From:   Vineet Gupta <vineet.gupta1@synopsys.com>
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Message-ID: <49f9edc9-87ee-1efc-58f8-b0d9a52c8a49@synopsys.com>
Date:   Wed, 19 Dec 2018 17:16:39 -0800
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On 12/19/18 9:04 AM, Eugeniy Paltsev wrote:
> As I can see x86 use print_vma_addr() in their show_signal_msg()
> function which allocate page with __get_free_page(GFP_NOWAIT);

Indeed with that the __get_free_page() lockdep splat is gone.

There's a different one now hence my other patch.

| [ARCLinux]# ./segv-null-ptr
| potentially unexpected fatal signal 11.
| BUG: sleeping function called from invalid context at kernel/fork.c:1011
| in_atomic(): 1, irqs_disabled(): 0, pid: 70, name: segv-null-ptr
| no locks held by segv-null-ptr/70.
| CPU: 0 PID: 70 Comm: segv-null-ptr Not tainted 4.18.0+ #69
|
| Stack Trace:
|  arc_unwind_core+0xcc/0x100
|  ___might_sleep+0x17a/0x190
|  mmput+0x16/0xb8
|  show_regs+0x52/0x310
|  get_signal+0x5ee/0x610
|  do_signal+0x2c/0x218
|  resume_user_mode_begin+0x90/0xd8