Hi all, Has anyone tried to use ftrace to debug upstream kernel? I tried today but the result is, the serial console hung after ftrace enabled(kernel is alive because the Magic SysRq works). My steps are: - Enable CONFIG_FUNCTION_TRACER in kernel config - Enter command: echo 0 > /sys/kernel/debug/tracing/tracing_on;echo function > /sys/kernel/debug/tracing/current_tracer;echo 1 > /proc/sys/kernel/ftrace_dump_on_oops - Then sometimes the serial console hangs right after you entered the command above, or hangs when you try to "cat /sys/kernel/debug/trace" I dumped some backtraces(check below, by invoking a system crash manually) and hope it helps: root@tegra-ubuntu:~# cat /sys/kernel/debug/tracing/trace [ 121.979682] SysRq : Dump ftrace buffer [ 121.983633] Dumping ftrace buffer: [ 121.987110] (ftrace buffer empty) [ 133.531569] SysRq : HELP : loglevel(0-9) reBoot Crash terminate-all-tasks(E) memory-full-oom-kill(F) kill-all-tasks(I) thaw-filesystems(J) saK show-backtrace-all-active-cpus(L) show-memory-usage(M) nice -all-RT-tasks(N) powerOff show-registers(P) show-all-timers(Q) unRaw Sync show-task-states(T) Unmount force-fb(V) show-blocked-tasks(W) dump-ftrace-buffer(Z) [ 141.131316] SysRq : Show Blocked State [ 168.123126] SysRq : Show backtrace of all active CPUs [ 172.514795] SysRq : Trigger a crash [ 172.518384] Unable to handle kernel NULL pointer dereference at virtual address 00000000 [ 172.526622] pgd = c0004000 [ 172.529380] [00000000] *pgd=00000000 [ 172.533041] Internal error: Oops: 817 [#1] PREEMPT SMP ARM [ 172.538627] Modules linked in: brcmfmac brcmutil [ 172.543382] CPU: 0 Not tainted (3.7.0-rc8-next-20121211-00002-g4cdade7-dirty #10) [ 172.551364] PC is at sysrq_handle_crash+0x38/0x48 [ 172.556157] LR is at sysrq_handle_crash+0x30/0x48 [ 172.560950] pc : [<c02a346c>] lr : [<c02a3464>] psr: 60000193 [ 172.560950] sp : c07d5df0 ip : c05a6edc fp : c082ed84 [ 172.572630] r10: 00000001 r9 : 00000000 r8 : 00000004 [ 172.577950] r7 : 60000193 r6 : c08054ec r5 : 00000063 r4 : c07f083c [ 172.584594] r3 : 00000000 r2 : 00000001 r1 : 60000193 r0 : c0831f18 [ 172.591238] Flags: nZCv IRQs off FIQs on Mode SVC_32 ISA ARM Segment kernel [ 172.598767] Control: 10c5387d Table: ada0804a DAC: 00000015 [ 172.604617] Process swapper/0 (pid: 0, stack limit = 0xc07d4238) [ 172.610734] Stack: (0xc07d5df0 to 0xc07d6000) [ 172.615172] 5de0: c02a3434 c02a3bd4 c0899ba0 00000100 [ 172.623499] 5e00: 00000000 c07d60c0 eda67e00 00000000 00000061 c02b7810 00989680 00000000 [ 172.631826] 5e20: ffffffeb 3b9aca00 00000000 c0899ba0 60000193 00000061 c0899c7c 00000000 [ 172.640153] 5e40: ed840400 c02b79d4 00000000 ed84040c 00000044 c02b5e28 ed8de4c0 ee008710 [ 172.648481] 5e60: 00000044 fe000100 c07d4000 00000000 00000000 c008dae0 00000000 c0078160 [ 172.656807] 5e80: ee008724 ee0086c0 c07d6144 ee0086c0 ee008710 ed8de4c0 fe000100 00000000 [ 172.665133] 5ea0: c07f00e0 00000001 00000000 c008dd5c ee0086c0 ee008710 00000000 c0090c04 [ 172.673459] 5ec0: 00000044 00000044 00000000 c008d420 c07d15e4 c000f0ec fe00010c c07dc458 [ 172.681786] 5ee0: c07d5f00 c0008724 c00706cc c03a22bc 60000013 ffffffff c07d5f34 c000e460 [ 172.690113] 5f00: c07d5f48 3b9aca00 28d50160 00000028 287abc00 00000028 c10b1558 c07d5f48 [ 172.698439] 5f20: 00000000 c07f00e0 00000001 00000000 000000ab c07d5f48 c00706cc c03a22bc [ 172.706765] 5f40: 60000013 ffffffff 28d50160 00000028 00000000 c10b1558 c10b1558 c07d4000 [ 172.715092] 5f60: 00000000 c05aa5e0 00000001 c082f0f4 c089bc38 c03a1e44 01400000 c07f00e0 [ 172.723420] 5f80: c0831f18 c07d4000 c0831a88 c07dc434 c05aa5e0 c07e0df0 412fc099 00000000 [ 172.731746] 5fa0: 00000000 c000f530 c07dd5e8 ffffffff c08319c0 c07c4ff0 c10ae000 c079f7ac [ 172.740072] 5fc0: ffffffff ffffffff c079f234 00000000 00000000 c07c4ff0 00000000 10c5387d [ 172.748399] 5fe0: c07dc430 c07c4fec c07e0de4 8000406a 00000000 80008078 00000000 00000000 [ 172.756736] [<c02a346c>] (sysrq_handle_crash+0x38/0x48) from [<c02a3bd4>] (__handle_sysrq+0x10c/0x17c) [ 172.766218] [<c02a3bd4>] (__handle_sysrq+0x10c/0x17c) from [<c02b7810>] (serial8250_rx_chars+0xd4/0x224) [ 172.780521] [<c02b7810>] (serial8250_rx_chars+0xd4/0x224) from [<c02b79d4>] (serial8250_handle_irq+0x74/0xa4) [ 172.795330] [<c02b79d4>] (serial8250_handle_irq+0x74/0xa4) from [<c02b5e28>] (serial8250_interrupt+0x48/0xb8) [ 172.810195] [<c02b5e28>] (serial8250_interrupt+0x48/0xb8) from [<c008dae0>] (handle_irq_event_percpu+0x74/0x2ac) [ 172.825355] [<c008dae0>] (handle_irq_event_percpu+0x74/0x2ac) from [<c008dd5c>] (handle_irq_event+0x44/0x64) [ 172.840216] [<c008dd5c>] (handle_irq_event+0x44/0x64) from [<c0090c04>] (handle_fasteoi_irq+0xa8/0x17c) [ 172.854697] [<c0090c04>] (handle_fasteoi_irq+0xa8/0x17c) from [<c008d420>] (generic_handle_irq+0x28/0x38) [ 172.869245] [<c008d420>] (generic_handle_irq+0x28/0x38) from [<c000f0ec>] (handle_IRQ+0x40/0x98) [ 172.882876] [<c000f0ec>] (handle_IRQ+0x40/0x98) from [<c0008724>] (gic_handle_irq+0x30/0x64) [ 172.896038] [<c0008724>] (gic_handle_irq+0x30/0x64) from [<c000e460>] (__irq_svc+0x40/0x70) [ 172.909149] Exception stack(0xc07d5f00 to 0xc07d5f48) [ 172.918976] 5f00: c07d5f48 3b9aca00 28d50160 00000028 287abc00 00000028 c10b1558 c07d5f48 [ 172.932036] 5f20: 00000000 c07f00e0 00000001 00000000 000000ab c07d5f48 c00706cc c03a22bc [ 172.945068] 5f40: 60000013 ffffffff [ 172.953335] [<c000e460>] (__irq_svc+0x40/0x70) from [<c03a22bc>] (cpuidle_wrap_enter+0x54/0xa8) [ 172.966987] [<c03a22bc>] (cpuidle_wrap_enter+0x54/0xa8) from [<c03a1e44>] (cpuidle_idle_call+0xe0/0x378) [ 172.981480] [<c03a1e44>] (cpuidle_idle_call+0xe0/0x378) from [<c000f530>] (cpu_idle+0xc4/0x118) [ 172.995199] [<c000f530>] (cpu_idle+0xc4/0x118) from [<c079f7ac>] (start_kernel+0x2a8/0x2f8) [ 173.008555] Code: 0a000000 e12fff33 e3a02001 e3a03000 (e5c32000) [ 173.019629] ---[ end trace 3b1f58dc14f4f716 ]--- [ 173.029269] Kernel panic - not syncing: Fatal exception in interrupt [ 173.041047] CPU3: stopping [ 173.048777] [<c00156a4>] (unwind_backtrace+0x0/0x100) from [<c0014850>] (handle_IPI+0x124/0x14c) [ 173.062741] [<c0014850>] (handle_IPI+0x124/0x14c) from [<c0008750>] (gic_handle_irq+0x5c/0x64) [ 173.076573] [<c0008750>] (gic_handle_irq+0x5c/0x64) from [<c000e460>] (__irq_svc+0x40/0x70) [ 173.090176] Exception stack(0xee093f38 to 0xee093f80) [ 173.100436] 3f20: ee093f80 3b9aca00 [ 173.113873] 3f40: 4832e9a0 00000028 236d8e78 00000027 c10cc558 ee093f80 00000001 c07f00e0 [ 173.127337] 3f60: 00000001 00000000 000000ab ee093f80 c00706cc c03a22bc 60000113 ffffffff [ 173.140826] [<c000e460>] (__irq_svc+0x40/0x70) from [<c03a22bc>] (cpuidle_wrap_enter+0x54/0xa8) [ 173.154858] [<c03a22bc>] (cpuidle_wrap_enter+0x54/0xa8) from [<c03a1e44>] (cpuidle_idle_call+0xe0/0x378) [ 173.169719] [<c03a1e44>] (cpuidle_idle_call+0xe0/0x378) from [<c000f530>] (cpu_idle+0xc4/0x118) [ 173.183789] [<c000f530>] (cpu_idle+0xc4/0x118) from [<8059f3e8>] (0x8059f3e8) [ 174.173667] SMP: failed to stop secondary CPUs [ 174.183428] drm_kms_helper: panic occurred, switching back to text console Mark -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More 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