Messages in this thread Patch in this message | | | From | John Ogness <> | Subject | [PATCH printk v2 06/11] printk: nbcon: Wire up nbcon console atomic flushing | Date | Wed, 20 Sep 2023 01:14:51 +0206 |
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From: Thomas Gleixner <tglx@linutronix.de>
Perform nbcon console atomic flushing at key call sites:
nbcon_atomic_exit() - When exiting from the outermost atomic printing section. If the priority was NBCON_PRIO_PANIC, attempt a second flush allowing unsafe hostile takeovers.
console_flush_on_panic() - Called from several call sites to trigger ringbuffer dumping in an urgent situation.
console_flush_on_panic() - Typically the panic() function will take care of atomic flushing the nbcon consoles on panic. However, there are several users of console_flush_on_panic() outside of panic().
printk_trigger_flush() - Used in urgent situations to trigger a dump in an irq_work context. However, the atomic flushing part happens in the calling context since an alternative context is not required.
Co-developed-by: John Ogness <john.ogness@linutronix.de> Signed-off-by: John Ogness <john.ogness@linutronix.de> Signed-off-by: Thomas Gleixner (Intel) <tglx@linutronix.de> --- kernel/printk/nbcon.c | 10 ++++++++++ kernel/printk/printk.c | 6 ++++++ 2 files changed, 16 insertions(+)
diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c index 2a9ff18fc78c..82e6a1678363 100644 --- a/kernel/printk/nbcon.c +++ b/kernel/printk/nbcon.c @@ -1092,6 +1092,11 @@ void nbcon_atomic_flush_all(void) * Return: The previous priority that needs to be fed into * the corresponding nbcon_atomic_exit() * Context: Any context. Disables migration. + * + * When within an atomic printing section, no atomic printing occurs. This + * is to allow all emergency messages to be dumped into the ringbuffer before + * flushing the ringbuffer. The actual atomic printing occurs when exiting + * the outermost atomic printing section. */ enum nbcon_prio nbcon_atomic_enter(enum nbcon_prio prio) { @@ -1130,8 +1135,13 @@ void nbcon_atomic_exit(enum nbcon_prio prio, enum nbcon_prio prev_prio) { struct nbcon_cpu_state *cpu_state; + __nbcon_atomic_flush_all(false); + cpu_state = nbcon_get_cpu_state(); + if (cpu_state->prio == NBCON_PRIO_PANIC) + __nbcon_atomic_flush_all(true); + /* * Undo the nesting of nbcon_atomic_enter() at the CPU state * priority. diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 6ef33cefa4d0..419c0fabc481 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -3159,6 +3159,8 @@ void console_flush_on_panic(enum con_flush_mode mode) console_srcu_read_unlock(cookie); } + nbcon_atomic_flush_all(); + console_flush_all(false, &next_seq, &handover); } @@ -3903,6 +3905,10 @@ void defer_console_output(void) void printk_trigger_flush(void) { + migrate_disable(); + nbcon_atomic_flush_all(); + migrate_enable(); + defer_console_output(); } -- 2.39.2
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