From: John Ogness Date: Thu, 14 Dec 2023 14:38:42 +0000 Subject: [PATCH 27/50] printk: nbcon: Assign priority based on CPU state Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.7/older/patches-6.7-rt6.tar.xz Use the current state of the CPU to determine which priority to assign to the printing context. Note: The uart_port wrapper, which is responsible for non-console- printing activities, will always use NORMAL priority. Signed-off-by: John Ogness Signed-off-by: Sebastian Andrzej Siewior --- kernel/printk/internal.h | 2 ++ kernel/printk/nbcon.c | 30 ++++++++++++++++++++++++++++-- 2 files changed, 30 insertions(+), 2 deletions(-) --- a/kernel/printk/internal.h +++ b/kernel/printk/internal.h @@ -79,6 +79,7 @@ void nbcon_seq_force(struct console *con bool nbcon_alloc(struct console *con); void nbcon_init(struct console *con); void nbcon_free(struct console *con); +enum nbcon_prio nbcon_get_default_prio(void); void nbcon_atomic_flush_all(void); bool nbcon_atomic_emit_next_record(struct console *con, bool *handover, int cookie); @@ -135,6 +136,7 @@ static inline void nbcon_seq_force(struc static inline bool nbcon_alloc(struct console *con) { return false; } static inline void nbcon_init(struct console *con) { } static inline void nbcon_free(struct console *con) { } +static inline enum nbcon_prio nbcon_get_default_prio(void) { return NBCON_PRIO_NONE; } static inline void nbcon_atomic_flush_all(void) { } static inline bool nbcon_atomic_emit_next_record(struct console *con, bool *handover, int cookie) { return false; } --- a/kernel/printk/nbcon.c +++ b/kernel/printk/nbcon.c @@ -962,6 +962,22 @@ static bool nbcon_atomic_emit_one(struct } /** + * nbcon_get_default_prio - The appropriate nbcon priority to use for nbcon + * printing on the current CPU + * + * Context: Any context which could not be migrated to another CPU. + * Return: The nbcon_prio to use for acquiring an nbcon console in this + * context for printing. + */ +enum nbcon_prio nbcon_get_default_prio(void) +{ + if (this_cpu_in_panic()) + return NBCON_PRIO_PANIC; + + return NBCON_PRIO_NORMAL; +} + +/** * nbcon_atomic_emit_next_record - Print one record for an nbcon console * using the write_atomic() callback * @con: The console to print on @@ -997,7 +1013,7 @@ bool nbcon_atomic_emit_next_record(struc cant_migrate(); ctxt->console = con; - ctxt->prio = NBCON_PRIO_NORMAL; + ctxt->prio = nbcon_get_default_prio(); progress = nbcon_atomic_emit_one(&wctxt); @@ -1043,7 +1059,6 @@ static void __nbcon_atomic_flush_all(u64 memset(ctxt, 0, sizeof(*ctxt)); ctxt->console = con; ctxt->spinwait_max_us = 2000; - ctxt->prio = NBCON_PRIO_NORMAL; /* * Atomic flushing does not use console driver @@ -1052,9 +1067,14 @@ static void __nbcon_atomic_flush_all(u64 * disabled to avoid being interrupted and then * calling into a driver that will deadlock trying * acquire console ownership. + * + * This also disables migration in order to get the + * current CPU priority. */ local_irq_save(irq_flags); + ctxt->prio = nbcon_get_default_prio(); + any_progress |= nbcon_atomic_emit_one(&wctxt); local_irq_restore(irq_flags); @@ -1166,6 +1186,9 @@ static inline bool uart_is_nbcon(struct * * If @up is an nbcon console, this console will be acquired and marked as * unsafe. Otherwise this function does nothing. + * + * nbcon consoles acquired via the port lock wrapper always use priority + * NBCON_PRIO_NORMAL. */ void nbcon_acquire(struct uart_port *up) { @@ -1200,6 +1223,9 @@ EXPORT_SYMBOL_GPL(nbcon_acquire); * * If @up is an nbcon console, the console will be marked as safe and * released. Otherwise this function does nothing. + * + * nbcon consoles acquired via the port lock wrapper always use priority + * NBCON_PRIO_NORMAL. */ void nbcon_release(struct uart_port *up) {