rv/rtapp/sleep: Make the error more informative for user

The rtapp/sleep monitor detects real-time tasks which go to sleep in an
real-time-unsafe manner. If this happen, the monitor triggers a trace event
in the sched_wakeup tracepoint's handler.

However, the invoking context of that trace event is not the most
informative, because of the stack trace of that event is the wakeup's code
path which is not very helpful:

74.669317: rv:error_sleep: condvar[254]: violation detected
    ltl_validate+0x345 ([kernel.kallsyms])
    handle_sched_wakeup+0x34 ([kernel.kallsyms])
    ttwu_do_activate+0xff ([kernel.kallsyms])
    sched_ttwu_pending+0x104 ([kernel.kallsyms])
    __flush_smp_call_function_queue+0x15b ([kernel.kallsyms])
    __sysvec_call_function_single+0x18 ([kernel.kallsyms])
    sysvec_call_function_single+0x66 ([kernel.kallsyms])
    asm_sysvec_call_function_single+0x1a ([kernel.kallsyms])
    pv_native_safe_halt+0xf ([kernel.kallsyms])
    default_idle+0x9 ([kernel.kallsyms])
    default_idle_call+0x33 ([kernel.kallsyms])
    do_idle+0x234 ([kernel.kallsyms])
    cpu_startup_entry+0x24 ([kernel.kallsyms])
    start_secondary+0xf8 ([kernel.kallsyms])
    common_startup_64+0x13e ([kernel.kallsyms])

What would be much more valuable is the stack trace of the task itself.

Instead of using the sched_wakeup tracepoint, use the sched_exit
tracepoint. This makes the event happen in the task's context, making
the stack trace far more informative for user:

rv:error_sleep: condvar[254]: violation detected
    ltl_validate+0x345 ([kernel.kallsyms])
    handle_sched_exit+0x39 ([kernel.kallsyms])
    __schedule+0x80f ([kernel.kallsyms])
    schedule+0x22 ([kernel.kallsyms])
    futex_do_wait+0x33 ([kernel.kallsyms])
    __futex_wait+0x8c ([kernel.kallsyms])
    futex_wait+0x73 ([kernel.kallsyms])
    do_futex+0xc6 ([kernel.kallsyms])
    __x64_sys_futex+0x121 ([kernel.kallsyms])
    do_syscall_64+0xf3 ([kernel.kallsyms])
    entry_SYSCALL_64_after_hwframe+0x77 ([kernel.kallsyms])
    __futex_abstimed_wait_common64+0xc6 (inlined)
    __futex_abstimed_wait_common+0xc6 (/usr/lib/x86_64-linux-gnu/libc.so.6)

Signed-off-by: Nam Cao <namcao@linutronix.de>
Reviewed-by: Gabriele Monaco <gmonaco@redhat.com>
Link: https://lore.kernel.org/r/d97b4b5c476e5792b6875ec9bbf8dc214f999516.1781852967.git.namcao@linutronix.de
Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>

0 files changed, 0 insertions, 0 deletions