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Date: Wed, 3 Jul 2019 21:14:36 +0200
From: Greg KH <gregkh@linuxfoundation.org>
To: Mathieu Poirier <mathieu.poirier@linaro.org>
Subject: Re: [PATCH 1/5] coresight: tmc-etr: Do not call smp_processor_id()
 from preemptible
Message-ID: <20190703191436.GB17519@kroah.com>
References: <20190620221237.3536-1-mathieu.poirier@linaro.org>
 <20190620221237.3536-2-mathieu.poirier@linaro.org>
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On Thu, Jun 20, 2019 at 04:12:33PM -0600, Mathieu Poirier wrote:
> From: Suzuki K Poulose <suzuki.poulose@arm.com>
> 
> During a perf session we try to allocate buffers on the "node" associated
> with the CPU the event is bound to. If it's not bound to a CPU, we use
> the current CPU node, using smp_processor_id(). However this is unsafe
> in a pre-emptible context and could generate the splats as below :
> 
>  BUG: using smp_processor_id() in preemptible [00000000] code: perf/1743
>  caller is alloc_etr_buf.isra.6+0x80/0xa0
>  CPU: 1 PID: 1743 Comm: perf Not tainted 5.1.0-rc6-147786-g116841e #344
>  Hardware name: ARM LTD ARM Juno Development Platform/ARM Juno Development Platform, BIOS EDK II Feb  1 2019
>   Call trace:
>    dump_backtrace+0x0/0x150
>    show_stack+0x14/0x20
>    dump_stack+0x9c/0xc4
>    debug_smp_processor_id+0x10c/0x110
>    alloc_etr_buf.isra.6+0x80/0xa0
>    tmc_alloc_etr_buffer+0x12c/0x1f0
>    etm_setup_aux+0x1c4/0x230
>    rb_alloc_aux+0x1b8/0x2b8
>    perf_mmap+0x35c/0x478
>    mmap_region+0x34c/0x4f0
>    do_mmap+0x2d8/0x418
>    vm_mmap_pgoff+0xd0/0xf8
>    ksys_mmap_pgoff+0x88/0xf8
>    __arm64_sys_mmap+0x28/0x38
>    el0_svc_handler+0xd8/0x138
>    el0_svc+0x8/0xc
> 
> Use NUMA_NO_NODE hint instead of using the current node for events
> not bound to CPUs.
> 
> Fixes: 855ab61c16bf70b646 ("coresight: tmc-etr: Refactor function tmc_etr_setup_perf_buf()")

This should be:
	Fixes: 855ab61c16bf ("coresight: tmc-etr: Refactor function tmc_etr_setup_perf_buf()")

Add:
	[core]
	        abbrev = 12

to your .gitconfig file, we only need 12 in the kernel tree.  For now :)

thanks,

greg k-h

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