9d05c18e8d
When enabling ftrace graph tracer, it gets the tracing clock in
ftrace_push_return_trace(). Eventually, it invokes riscv_sched_clock()
to get the clock value. If riscv_sched_clock() isn't marked with
'notrace', it will call ftrace_push_return_trace() and cause infinite
loop.
The result of failure as follow:
command: echo function_graph >current_tracer
[ 46.176787] Unable to handle kernel paging request at virtual address ffffffe04fb38c48
[ 46.177309] Oops [#1]
[ 46.177478] Modules linked in:
[ 46.177770] CPU: 0 PID: 256 Comm: $d Not tainted 5.5.0-rc1 #47
[ 46.177981] epc: ffffffe00035e59a ra : ffffffe00035e57e sp : ffffffe03a7569b0
[ 46.178216] gp : ffffffe000d29b90 tp : ffffffe03a756180 t0 : ffffffe03a756968
[ 46.178430] t1 : ffffffe00087f408 t2 : ffffffe03a7569a0 s0 : ffffffe03a7569f0
[ 46.178643] s1 : ffffffe00087f408 a0 : 0000000ac054cda4 a1 : 000000000087f411
[ 46.178856] a2 : 0000000ac054cda4 a3 : 0000000000373ca0 a4 : ffffffe04fb38c48
[ 46.179099] a5 : 00000000153e22a8 a6 : 00000000005522ff a7 : 0000000000000005
[ 46.179338] s2 : ffffffe03a756a90 s3 : ffffffe00032811c s4 : ffffffe03a756a58
[ 46.179570] s5 : ffffffe000d29fe0 s6 : 0000000000000001 s7 : 0000000000000003
[ 46.179809] s8 : 0000000000000003 s9 : 0000000000000002 s10: 0000000000000004
[ 46.180053] s11: 0000000000000000 t3 : 0000003fc815749c t4 : 00000000000efc90
[ 46.180293] t5 : ffffffe000d29658 t6 : 0000000000040000
[ 46.180482] status: 0000000000000100 badaddr: ffffffe04fb38c48 cause: 000000000000000f
Signed-off-by: Zong Li <zong.li@sifive.com>
Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
[paul.walmsley@sifive.com: cleaned up patch description]
Fixes: 92e0d143fd ("clocksource/drivers/riscv_timer: Provide the sched_clock")
Cc: stable@vger.kernel.org
Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.