From 40eea5abbb9ccae6df55dfd94c3c85c023e2521b Mon Sep 17 00:00:00 2001 From: Florian Rommel Date: Thu, 25 Apr 2024 17:35:01 +0200 Subject: [PATCH] scripts/gdb: fix detection of current CPU in KGDB Directly read the current CPU number from the kgdb_active variable. Before, the active CPU was obtained through the current task, which required searching the task list for the pid of GDB's selected thread. Obtaining the pid was buggy: GDB may use selected_thread().ptid[1] (LWPID) instead of .ptid[2] (TID) to store the threads pid; see https://sourceware.org/gdb/current/onlinedocs/gdb.html/Threads-In-Python.html As a result, the detection could return the wrong CPU number, leading to incorrect results for $lx_per_cpu and $lx_current. As a side effect, the patch significantly speeds up $lx_per_cpu and $lx_current in KGDB by avoiding the task-list iteration. Link: https://lkml.kernel.org/r/20240425153501.749966-5-mail@florommel.de Signed-off-by: Florian Rommel Cc: Andrew Jones Cc: Deepak Gupta Cc: Jan Kiszka Cc: Kieran Bingham Cc: Kuan-Ying Lee Cc: Palmer Dabbelt Signed-off-by: Andrew Morton --- scripts/gdb/linux/cpus.py | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-) diff --git a/scripts/gdb/linux/cpus.py b/scripts/gdb/linux/cpus.py index 2b51a3abd3639..2f11c4f9c345a 100644 --- a/scripts/gdb/linux/cpus.py +++ b/scripts/gdb/linux/cpus.py @@ -26,11 +26,7 @@ def get_current_cpu(): if utils.get_gdbserver_type() == utils.GDBSERVER_QEMU: return gdb.selected_thread().num - 1 elif utils.get_gdbserver_type() == utils.GDBSERVER_KGDB: - tid = gdb.selected_thread().ptid[2] - if tid > (0x100000000 - MAX_CPUS - 2): - return 0x100000000 - tid - 2 - else: - return tasks.get_thread_info(tasks.get_task_by_pid(tid))['cpu'] + return gdb.parse_and_eval("kgdb_active.counter") else: raise gdb.GdbError("Sorry, obtaining the current CPU is not yet " "supported with this gdb server.")