linux-kernel - RE: [PATCH v2 2/2] tracing: Fix for non-continuous cpu ids

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Date:	Tue, 14 Jul 2015 10:12:47 +0000
From:	Gil Fruchter <gilf@...hip.com>
To:	Steven Rostedt <rostedt@...dmis.org>
CC:	"mingo@...hat.com" <mingo@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Gilad Ben Yossef <giladb@...hip.com>,
	"Chris Metcalf" <cmetcalf@...hip.com>,
	Noam Camus <noamc@...hip.com>
Subject: RE: [PATCH v2 2/2] tracing: Fix for non-continuous cpu ids

On Monday, July 13, 2015 7:12 PM
Steven Rostedt <rostedt@...dmis.org> wrote:

> On Tue, 9 Jun 2015 10:32:35 +0300
> Gil Fruchter <gilf@...hip.com> wrote:
>
> > Currently exception occures due to access beyond buffer_iter range 
> > while using index of cpu bigger than num_possible_cpus().
> > Below there is an example for such exception when we use cpus 
> >  0,1,16,17.
> >
> > In order to fix buffer allocation size for non-continuous cpu ids we 
> > allocate according to the max cpu id and not according to the amount 
> > of possible cpus.
> >
> > Example:
> >   $ cat /sys/kernel/debug/tracing/per_cpu/cpu1/trace
> >   Path: /bin/busybox
> >   CPU: 0 PID: 82 Comm: cat Not tainted 4.0.0 #29
> >   task: 80734c80 ti: 80012000 task.ti: 80012000
> >
> >   [ECR   ]: 0x00220100 => Invalid Read @ 0x00000000 by insn @ 0x800abafc
> >   [EFA   ]: 0x00000000
> >   [BLINK ]: ring_buffer_read_finish+0x24/0x64
> >   [ERET  ]: rb_check_pages+0x20/0x188
> >   [STAT32]: 0x00001a00 :
> >   BTA: 0x800abafc  SP: 0x80013f0c  FP: 0x57719cf8
> >   LPS: 0x200036b4 LPE: 0x200036b8 LPC: 0x00000000
> >   r00: 0x8002aca0 r01: 0x00001606 r02: 0x00000000
> >   r03: 0x00000001 r04: 0x00000000 r05: 0x804b4954
> >   r06: 0x00030003 r07: 0x8002a260 r08: 0x00000286
> >   r09: 0x00080002 r10: 0x00001006 r11: 0x807351a4
> >   r12: 0x00000001
> >
> >   Stack Trace:
> >     rb_check_pages+0x20/0x188
> >     ring_buffer_read_finish+0x24/0x64
> >     tracing_release+0x4e/0x170
> >     __fput+0x62/0x158
> >     task_work_run+0xa2/0xd4
> >     do_notify_resume+0x52/0x7c
> >     resume_user_mode_begin+0xdc/0xe0
> >
> > Signed-off-by: Noam Camus <noamc@...hip.com>
>
> Why Noam's SoB tag? Did he author it?
>
> -- Steve
>

He didn't author it, but we worked on this issue together.

Gil.
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