diff options
| -rw-r--r-- | include/linux/console.h | 4 | ||||
| -rw-r--r-- | kernel/printk/internal.h | 1 | ||||
| -rw-r--r-- | kernel/printk/nbcon.c | 75 |
3 files changed, 79 insertions, 1 deletions
diff --git a/include/linux/console.h b/include/linux/console.h index 3706f944de46..9a13f91b0c43 100644 --- a/include/linux/console.h +++ b/include/linux/console.h @@ -553,10 +553,14 @@ static inline bool console_is_registered(const struct console *con) hlist_for_each_entry(con, &console_list, node) #ifdef CONFIG_PRINTK +extern void nbcon_cpu_emergency_enter(void); +extern void nbcon_cpu_emergency_exit(void); extern bool nbcon_can_proceed(struct nbcon_write_context *wctxt); extern bool nbcon_enter_unsafe(struct nbcon_write_context *wctxt); extern bool nbcon_exit_unsafe(struct nbcon_write_context *wctxt); #else +static inline void nbcon_cpu_emergency_enter(void) { } +static inline void nbcon_cpu_emergency_exit(void) { } static inline bool nbcon_can_proceed(struct nbcon_write_context *wctxt) { return false; } static inline bool nbcon_enter_unsafe(struct nbcon_write_context *wctxt) { return false; } static inline bool nbcon_exit_unsafe(struct nbcon_write_context *wctxt) { return false; } diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h index ba2e0f1940bd..8e36d8695f81 100644 --- a/kernel/printk/internal.h +++ b/kernel/printk/internal.h @@ -182,6 +182,7 @@ static inline void printk_get_console_flush_type(struct console_flush_type *ft) switch (nbcon_get_default_prio()) { case NBCON_PRIO_NORMAL: + case NBCON_PRIO_EMERGENCY: if (have_nbcon_console && !have_boot_console) ft->nbcon_atomic = true; diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c index 18488d6c17c0..92ac5c590927 100644 --- a/kernel/printk/nbcon.c +++ b/kernel/printk/nbcon.c @@ -972,6 +972,36 @@ update_con: return nbcon_context_exit_unsafe(ctxt); } +/* Track the nbcon emergency nesting per CPU. */ +static DEFINE_PER_CPU(unsigned int, nbcon_pcpu_emergency_nesting); +static unsigned int early_nbcon_pcpu_emergency_nesting __initdata; + +/** + * nbcon_get_cpu_emergency_nesting - Get the per CPU emergency nesting pointer + * + * Context: For reading, any context. For writing, any context which could + * not be migrated to another CPU. + * Return: Either a pointer to the per CPU emergency nesting counter of + * the current CPU or to the init data during early boot. + * + * The function is safe for reading per-CPU variables in any context because + * preemption is disabled if the current CPU is in the emergency state. See + * also nbcon_cpu_emergency_enter(). + */ +static __ref unsigned int *nbcon_get_cpu_emergency_nesting(void) +{ + /* + * The value of __printk_percpu_data_ready gets set in normal + * context and before SMP initialization. As a result it could + * never change while inside an nbcon emergency section. + */ + if (!printk_percpu_data_ready()) + return &early_nbcon_pcpu_emergency_nesting; + + /* Open code this_cpu_ptr() without checking migration. */ + return per_cpu_ptr(&nbcon_pcpu_emergency_nesting, raw_smp_processor_id()); +} + /** * nbcon_get_default_prio - The appropriate nbcon priority to use for nbcon * printing on the current CPU @@ -981,13 +1011,20 @@ update_con: * context for printing. * * The function is safe for reading per-CPU data in any context because - * preemption is disabled if the current CPU is in the panic state. + * preemption is disabled if the current CPU is in the emergency or panic + * state. */ enum nbcon_prio nbcon_get_default_prio(void) { + unsigned int *cpu_emergency_nesting; + if (this_cpu_in_panic()) return NBCON_PRIO_PANIC; + cpu_emergency_nesting = nbcon_get_cpu_emergency_nesting(); + if (*cpu_emergency_nesting) + return NBCON_PRIO_EMERGENCY; + return NBCON_PRIO_NORMAL; } @@ -1247,6 +1284,42 @@ void nbcon_atomic_flush_unsafe(void) } /** + * nbcon_cpu_emergency_enter - Enter an emergency section where printk() + * messages for that CPU are flushed directly + * + * Context: Any context. Disables preemption. + * + * When within an emergency section, printk() calls will attempt to flush any + * pending messages in the ringbuffer. + */ +void nbcon_cpu_emergency_enter(void) +{ + unsigned int *cpu_emergency_nesting; + + preempt_disable(); + + cpu_emergency_nesting = nbcon_get_cpu_emergency_nesting(); + (*cpu_emergency_nesting)++; +} + +/** + * nbcon_cpu_emergency_exit - Exit an emergency section + * + * Context: Within an emergency section. Enables preemption. + */ +void nbcon_cpu_emergency_exit(void) +{ + unsigned int *cpu_emergency_nesting; + + cpu_emergency_nesting = nbcon_get_cpu_emergency_nesting(); + + if (!WARN_ON_ONCE(*cpu_emergency_nesting == 0)) + (*cpu_emergency_nesting)--; + + preempt_enable(); +} + +/** * nbcon_alloc - Allocate and init the nbcon console specific data * @con: Console to initialize * |