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Date: Sun, 29 Nov 2009 18:20:35 -0800
Message-ID: <110c8b2e0911291820t410c2908t90dfc97b340b9725@mail.gmail.com>
Subject: ftrace not showing stack trace data during boot processes
From: Subodh Nijsure <nijsure.subodh@gmail.com>
To: linux-kernel@vger.kernel.org
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I am trying to debug some boot sequences during kernel bootup and
trying to use ftrace to discover function flow.

I am booting kernel with following options.

stacktrace trace_buf_size=30M ftrace=function
ftrace_filter=do_sync_write,usbfs*,ext2_*,vfs_write,blkdev_*,vfs_write,sys_write
ftrace_notrace=ext2_permission

I have compiled kernel with following options

CONFIG_NOP_TRACER=y
CONFIG_HAVE_FUNCTION_TRACER=y
CONFIG_HAVE_DYNAMIC_FTRACE=y
CONFIG_HAVE_FTRACE_MCOUNT_RECORD=y
CONFIG_RING_BUFFER=y
CONFIG_TRACING=y
CONFIG_FUNCTION_TRACER=y
CONFIG_SYSPROF_TRACER=y
CONFIG_CONTEXT_SWITCH_TRACER=y
CONFIG_BOOT_TRACER=y
CONFIG_STACK_TRACER=y
CONFIG_DYNAMIC_FTRACE=y
CONFIG_FTRACE_MCOUNT_RECORD=y

However when I look at  /sys/kernel/debug/tracing/trace

I see output similar to this and  I don't see the "stack trace"
            init-1     [000]    65.317499: sys_write <-sysenter_do_call
            init-1     [000]    65.317504: vfs_write <-sys_write
            init-1     [000]    65.317617: sys_write <-sysenter_do_call
            init-1     [000]    65.317619: vfs_write <-sys_write

Is there option I am missing while compiling kernel or some part of
kernel parameters is missing? Is there way to explicitly specify
iter_ctrl on kernel boot cmdline?

/Subodh