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.
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| @@ -26,11 +26,7 @@ def get_current_cpu(): · 25 unmodified lines | ||
| 26 | 26 | if utils.get_gdbserver_type() == utils.GDBSERVER_QEMU: |
| 27 | 27 | return gdb.selected_thread().num - 1 |
| 28 | 28 | elif utils.get_gdbserver_type() == utils.GDBSERVER_KGDB: |
| 29 | − tid = gdb.selected_thread().ptid[2] | |
| 30 | − if tid > (0x100000000 - MAX_CPUS - 2): | |
| 31 | − return 0x100000000 - tid - 2 | |
| 32 | − else: | |
| 33 | − return tasks.get_thread_info(tasks.get_task_by_pid(tid))['cpu'] | |
| 29 | + return gdb.parse_and_eval("kgdb_active.counter") | |
| 34 | 30 | else: |
| 35 | 31 | raise gdb.GdbError("Sorry, obtaining the current CPU is not yet " |
| 36 | 32 | "supported with this gdb server.") |