diff options
| -rw-r--r-- | include/linux/kdb.h | 16 | ||||
| -rw-r--r-- | kernel/printk/nbcon.c | 6 |
2 files changed, 21 insertions, 1 deletions
diff --git a/include/linux/kdb.h b/include/linux/kdb.h index ecbf819deeca..741c58e86431 100644 --- a/include/linux/kdb.h +++ b/include/linux/kdb.h @@ -14,6 +14,7 @@ */ #include <linux/list.h> +#include <linux/smp.h> /* Shifted versions of the command enable bits are be used if the command * has no arguments (see kdb_check_flags). This allows commands, such as @@ -207,11 +208,26 @@ static inline const char *kdb_walk_kallsyms(loff_t *pos) /* Dynamic kdb shell command registration */ extern int kdb_register(kdbtab_t *cmd); extern void kdb_unregister(kdbtab_t *cmd); + +/* Return true when KDB as locked for printing a message on this CPU. */ +static inline +bool kdb_printf_on_this_cpu(void) +{ + /* + * We can use raw_smp_processor_id() here because the task could + * not get migrated when KDB has locked for printing on this CPU. + */ + return unlikely(READ_ONCE(kdb_printf_cpu) == raw_smp_processor_id()); +} + #else /* ! CONFIG_KGDB_KDB */ static inline __printf(1, 2) int kdb_printf(const char *fmt, ...) { return 0; } static inline void kdb_init(int level) {} static inline int kdb_register(kdbtab_t *cmd) { return 0; } static inline void kdb_unregister(kdbtab_t *cmd) {} + +static inline bool kdb_printf_on_this_cpu(void) { return false; } + #endif /* CONFIG_KGDB_KDB */ enum { KDB_NOT_INITIALIZED, diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c index e1bf5409cb6b..5be018493909 100644 --- a/kernel/printk/nbcon.c +++ b/kernel/printk/nbcon.c @@ -10,6 +10,7 @@ #include <linux/export.h> #include <linux/init.h> #include <linux/irqflags.h> +#include <linux/kdb.h> #include <linux/kthread.h> #include <linux/minmax.h> #include <linux/panic.h> @@ -249,13 +250,16 @@ static int nbcon_context_try_acquire_direct(struct nbcon_context *ctxt, * since all non-panic CPUs are stopped during panic(), it * is safer to have them avoid gaining console ownership. * - * If this acquire is a reacquire (and an unsafe takeover + * One exception is when kdb has locked for printing on this CPU. + * + * Second exception is a reacquire (and an unsafe takeover * has not previously occurred) then it is allowed to attempt * a direct acquire in panic. This gives console drivers an * opportunity to perform any necessary cleanup if they were * interrupted by the panic CPU while printing. */ if (panic_on_other_cpu() && + !kdb_printf_on_this_cpu() && (!is_reacquire || cur->unsafe_takeover)) { return -EPERM; } |