On 11/21/2016 04:26 PM, He Zhe wrote: > > On 11/19/2016 12:35 AM, Steven Rostedt wrote: >> On Fri, 18 Nov 2016 14:23:24 +0800 >> He Zhe <zhe.he@xxxxxxxxxxxxx> wrote: >> >>> Hi, >>> >>> I'm using 4.8.6-rt5 and find the following issue on nxp-t4xxx board/qemuppc/qemux86-64. >>> When executing "echo function_graph > /sys/kernel/debug/tracing/current_tracer" the system hangs. >>> I traced the kernel to where it dies but don't know how to fix. Please help. Thank you. >>> >>> (gdb) b ftrace_startup >>> >>> ... >>> >>> Run till exit from #0 ftrace_startup (ops=0xc0cf1704 <graph_ops>, command=8) at /PATH/TO/kernel/trace/ftrace.c:2653 >>> 0xc00eb768 in register_ftrace_graph (retfunc=0xc010186c <trace_graph_return>, entryfunc=0xc01014c4 <trace_graph_entry>) >>> at /PATH/TO/kernel-source/kernel/trace/ftrace.c:5908 >>> 5908 ret = ftrace_startup(&graph_ops, FTRACE_START_FUNC_RET); >>> Value returned is $1 = 0 >>> (gdb) l >>> 5903 */ >>> 5904 __ftrace_graph_entry = entryfunc; >>> 5905 ftrace_graph_entry = ftrace_graph_entry_test; >>> 5906 update_function_graph_func(); >>> 5907 >>> 5908 ret = ftrace_startup(&graph_ops, FTRACE_START_FUNC_RET); >>> 5909 out: >>> 5910 mutex_unlock(&ftrace_lock); >>> 5911 return ret; >>> 5912 } >>> (gdb) n >>> 5910 mutex_unlock(&ftrace_lock); >>> (gdb) n >>> >>> hangs... >>> >> Can't you get a backtrace from this? It's running under qemu right? So >> it should be able to break it and see where it is at. >> >> Note, my PowerPC box has just died, so I'm no longer able to work on >> it, and don't have time to set up a qemu ppc image at the moment. > Thanks you. > So far we've found it happens on nxp-t4020(ppc) nxp-ls1021a(arma7) intel-x86 qemuppc qemux86-64. > Here is my backtrace and the config is attached. > > (gdb) l > 5905 ftrace_graph_entry = ftrace_graph_entry_test; > 5906 update_function_graph_func(); > 5907 > 5908 ret = ftrace_startup(&graph_ops, FTRACE_START_FUNC_RET); > 5909 out: > 5910 mutex_unlock(&ftrace_lock); <--- dies here > 5911 return ret; > 5912 } > 5913 > 5914 void unregister_ftrace_graph(void) > (gdb) bt > #0 register_ftrace_graph (retfunc=0xc0101548 <trace_graph_return>, entryfunc=0xc01011a0 <trace_graph_entry>) > at /PATH/kernel/trace/ftrace.c:5910 > #1 0xc0100e3c in graph_trace_init (tr=<optimized out>) at /PATH/kernel/trace/trace_functions_graph.c:461 > #2 0xc00f46cc in tracer_init (tr=<optimized out>, t=<optimized out>) at /PATH/kernel/trace/trace.c:4588 > #3 tracing_set_tracer (tr=0xc0cdd970 <global_trace>, buf=0xca347e18 "function_graph") > at /PATH/kernel/trace/trace.c:4849 > #4 0xc00f4868 in tracing_set_trace_write (filp=<optimized out>, ubuf=<optimized out>, cnt=3392437791, ppos=0xca347f18) > at /PATH/kernel/trace/trace.c:4887 > #5 0xc01b77c0 in __vfs_write (file=<optimized out>, p=<optimized out>, count=<optimized out>, pos=<optimized out>) > at /PATH/fs/read_write.c:510 > #6 0xc01b88ec in vfs_write (file=0xcd9e2000, buf=0x1011ff80 "function_graph\n", count=15, pos=0xca347f18) > at /PATH/fs/read_write.c:560 > #7 0xc01b9968 in SYSC_write (count=<optimized out>, buf=<optimized out>, fd=<optimized out>) > at /PATH/fs/read_write.c:607 > #8 SyS_write (fd=<optimized out>, buf=269614976, count=15) at /PATH/fs/read_write.c:599 > #9 0xc00127e4 in syscall_dotrace_cont () at /PATH/arch/powerpc/kernel/entry_32.S:353 And I've tried on "a7fac75 Linux 4.8.1" and the latest linux-4.8.y-rt-rebase branch.They have the same issue. Zhe > > Zhe > >> -- Steve >> -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
