From mboxrd@z Thu Jan 1 00:00:00 1970 From: jungseoklee85@gmail.com (Jungseok Lee) Date: Tue, 21 Jul 2015 23:34:21 +0900 Subject: [RFC 2/3] arm64: refactor save_stack_trace() In-Reply-To: <55AE1E5F.6060407@linaro.org> References: <20150716102405.2cc8c406@gandalf.local.home> <12F47692-3010-4886-B87D-3D7820609177@gmail.com> <20150716113115.45a17f17@gandalf.local.home> <20150716121658.7982fdf5@gandalf.local.home> <20150717124054.GE26091@leverpostej> <20150717090009.720f6bd0@gandalf.local.home> <77EA0F10-D5F6-48BD-8652-3B979A978659@gmail.com> <20150717104144.6588b2f7@gandalf.local.home> <0886A996-40E1-49E9-823C-85E55A858716@gmail.com> <1357EA74-B972-4B99-ADB0-BC7E8F06DDB5@gmail.com> <20150720162004.GL9908@arm.com> <55AD89FE.1010706@linaro.org> <55AE1E5F.6060407@linaro.org> Message-ID: <39628AC3-A593-4E48-89A5-D95F22734009@gmail.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Jul 21, 2015, at 7:26 PM, AKASHI Takahiro wrote: > On 07/21/2015 08:53 AM, AKASHI Takahiro wrote: >> Hi >> >> So i don't have to repost my patch here. Please use the original >> commit log message[1/3] as is. >> But please keep in mind that there is still an issue that I mentioned >> in the cover letter; 'Size' field is inaccurate. >> = >> + >> and >> = + >> - >> where "dynamic" means, for example, a variable allocated like the below: >> int foo(int num) { >> int array[num]; >> ... >> } >> (See more details in my ascii art.) >> >> Such usage is seldom seen in the kernel, and is >> likely equal to . In other words, we will >> see one-line *displacement* in most cases. > > Well, I have a quick fix now, but it looks ugly. AFAIU, stack_max_size would be more accurate if a separate stack is introduced for interrupt context. However, it might be unnecessary at this point due to complexity. > In addition, I found another issue; With function_graph tracer, > the output is like: > # cat /sys/kernel/tracing/stack_trace > Depth Size Location (78 entries) > ----- ---- -------- > 0) 6184 32 update_min_vruntime+0x14/0x74 > 1) 6152 48 update_curr+0x6c/0x150 > 2) 6104 128 enqueue_task_fair+0x2f4/0xb9c > 3) 5976 48 enqueue_task+0x48/0x90 > ... > 18) 5160 112 hrtimer_interrupt+0xa0/0x214 > 19) 5048 32 arch_timer_handler_phys+0x38/0x48 > 20) 5016 0 ftrace_graph_caller+0x2c/0x30 > 21) 5016 64 ftrace_graph_caller+0x2c/0x30 > 22) 4952 32 ftrace_graph_caller+0x2c/0x30 > 23) 4920 64 ftrace_graph_caller+0x2c/0x30 > ... > > Since, with function_graph tracer, we modify LR register in a stack frame > when we enter into a function, we have to manage such special cases > in save_stack_trace() or check_stack() as x86 does in > print_ftrace_graph_addr(). I should have run it with function_graph. The issue is reproduced easily on my environment. I don't see other issues yet when enabling other tracers. Best Regards Jungseok Lee