The live debug can be enabled for ppc64. For inactive tasks, it can show
the stack unwinding results:
crash> sys
KERNEL: /usr/lib/debug/lib/modules/5.14.0-425.el9.ppc64le/vmlinux
DUMPFILE: /proc/kcore
...
crash> set 1
crash> bt
PID: 1 TASK: c0000000035fc900 CPU: 1 COMMAND: "systemd"
#0 [c00000000369fa60] __schedule at c000000000fc3c58
#1 [c00000000369fb20] schedule at c000000000fc411c
#2 [c00000000369fb50] schedule_hrtimeout_range_clock at c000000000fcd2a4
#3 [c00000000369fc00] ep_poll at c00000000063640c
#4 [c00000000369fcf0] do_epoll_wait at c000000000636584
#5 [c00000000369fd40] sys_epoll_wait at c000000000636608
#6 [c00000000369fdb0] system_call_exception at c00000000002e994
#7 [c00000000369fe10] system_call_vectored_common at c00000000000bfe8
crash> gdb bt
#0 0xc000000000fc3c58 in context_switch ...
#1 __schedule ...
#2 0xc000000000fc411c in schedule_loop ...
#3 schedule ...
#4 0xc000000000fcd2a4 in schedule_hrtimeout_range_clock ...
#5 0xc00000000063640c in ep_poll ...
#6 0xc000000000636584 in do_epoll_wait ...
#7 0xc000000000636608 in __do_sys_epoll_wait ...
#8 __se_sys_epoll_wait ...
#9 0xc00000000002e994 in system_call_exception ...
#10 0xc00000000000bfe8 in system_call_vectored_common ...
However for active tasks in live mode, stack unwind will fail. The behaviour
is similar for "bt" and "gdb bt":
crash> ps
PID PPID CPU TASK ST %MEM VSZ RSS COMM
0 0 0 c000000002af6380 RU 0.0 0 0 [swapper/0]
> 0 0 1 c0000000035f9000 RU 0.0 0 0 [swapper/1]
> 0 0 2 c0000000035f0180 RU 0.0 0 0 [swapper/2]
...
crash> set c0000000035f0180
crash> bt
PID: 0 TASK: c0000000035f0180 CPU: 2 COMMAND: "swapper/2"
(active)
crash> gdb bt
#0 0xc000000003847d50 in ?? ()
#1 0x0000000000000000 in ?? ()
Signed-off-by: Tao Liu <ltao@xxxxxxxxxx>
---
ppc64.c | 5 -----
1 file changed, 5 deletions(-)
diff --git a/ppc64.c b/ppc64.c
index f86d951..a87e621 100644
--- a/ppc64.c
+++ b/ppc64.c
@@ -2516,11 +2516,6 @@ ppc64_get_cpu_reg(int cpu, int regno, const char *name, int size,
ulong ip, sp;
bool ret = FALSE;
- if (LIVE()) {
- /* doesn't support reading registers in live dump */
- return FALSE;
- }
-
/* Currently only handling registers available in ppc64_pt_regs:
*
* 0-31: r0-r31
--
2.40.1
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