diff options
| -rw-r--r-- | arch/um/kernel/kmsg_dump.c | 2 | ||||
| -rw-r--r-- | drivers/tty/serial/kgdboc.c | 1 | ||||
| -rw-r--r-- | include/linux/console.h | 55 | ||||
| -rw-r--r-- | include/linux/kdb.h | 16 | ||||
| -rw-r--r-- | kernel/debug/kdb/kdb_io.c | 47 | ||||
| -rw-r--r-- | kernel/printk/internal.h | 45 | ||||
| -rw-r--r-- | kernel/printk/nbcon.c | 71 | ||||
| -rw-r--r-- | kernel/printk/printk.c | 12 |
8 files changed, 176 insertions, 73 deletions
diff --git a/arch/um/kernel/kmsg_dump.c b/arch/um/kernel/kmsg_dump.c index 419021175272..fc0f543d1d8e 100644 --- a/arch/um/kernel/kmsg_dump.c +++ b/arch/um/kernel/kmsg_dump.c @@ -31,7 +31,7 @@ static void kmsg_dumper_stdout(struct kmsg_dumper *dumper, * expected to output the crash information. */ if (strcmp(con->name, "ttynull") != 0 && - (console_srcu_read_flags(con) & CON_ENABLED)) { + console_is_usable(con, console_srcu_read_flags(con), true)) { break; } } diff --git a/drivers/tty/serial/kgdboc.c b/drivers/tty/serial/kgdboc.c index 85f6c5a76e0f..5a955c80a853 100644 --- a/drivers/tty/serial/kgdboc.c +++ b/drivers/tty/serial/kgdboc.c @@ -577,7 +577,6 @@ static int __init kgdboc_earlycon_init(char *opt) console_list_lock(); for_each_console(con) { if (con->write && con->read && - (con->flags & (CON_BOOT | CON_ENABLED)) && (!opt || !opt[0] || strcmp(con->name, opt) == 0)) break; } diff --git a/include/linux/console.h b/include/linux/console.h index 8f10d0a85bb4..d17f1f525bec 100644 --- a/include/linux/console.h +++ b/include/linux/console.h @@ -19,6 +19,7 @@ #include <linux/irq_work.h> #include <linux/rculist.h> #include <linux/rcuwait.h> +#include <linux/smp.h> #include <linux/types.h> #include <linux/vesa.h> @@ -602,16 +603,70 @@ static inline bool console_is_registered(const struct console *con) 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 void nbcon_write_context_set_buf(struct nbcon_write_context *wctxt, + char *buf, unsigned int len); extern bool nbcon_enter_unsafe(struct nbcon_write_context *wctxt); extern bool nbcon_exit_unsafe(struct nbcon_write_context *wctxt); extern void nbcon_reacquire_nobuf(struct nbcon_write_context *wctxt); +extern bool nbcon_kdb_try_acquire(struct console *con, + struct nbcon_write_context *wctxt); +extern void nbcon_kdb_release(struct nbcon_write_context *wctxt); + +/* + * Check if the given console is currently capable and allowed to print + * records. Note that this function does not consider the current context, + * which can also play a role in deciding if @con can be used to print + * records. + */ +static inline bool console_is_usable(struct console *con, short flags, bool use_atomic) +{ + if (!(flags & CON_ENABLED)) + return false; + + if ((flags & CON_SUSPENDED)) + return false; + + if (flags & CON_NBCON) { + /* The write_atomic() callback is optional. */ + if (use_atomic && !con->write_atomic) + return false; + + /* + * For the !use_atomic case, @printk_kthreads_running is not + * checked because the write_thread() callback is also used + * via the legacy loop when the printer threads are not + * available. + */ + } else { + if (!con->write) + return false; + } + + /* + * Console drivers may assume that per-cpu resources have been + * allocated. So unless they're explicitly marked as being able to + * cope (CON_ANYTIME) don't call them until this CPU is officially up. + */ + if (!cpu_online(raw_smp_processor_id()) && !(flags & CON_ANYTIME)) + return false; + + return true; +} + #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 void nbcon_write_context_set_buf(struct nbcon_write_context *wctxt, + char *buf, unsigned int len) { } 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; } static inline void nbcon_reacquire_nobuf(struct nbcon_write_context *wctxt) { } +static inline bool nbcon_kdb_try_acquire(struct console *con, + struct nbcon_write_context *wctxt) { return false; } +static inline void nbcon_kdb_release(struct nbcon_write_context *wctxt) { } +static inline bool console_is_usable(struct console *con, short flags, + bool use_atomic) { return false; } #endif extern int console_set_on_cmdline; 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/debug/kdb/kdb_io.c b/kernel/debug/kdb/kdb_io.c index b12b9db75c1d..61c1690058ed 100644 --- a/kernel/debug/kdb/kdb_io.c +++ b/kernel/debug/kdb/kdb_io.c @@ -589,24 +589,41 @@ static void kdb_msg_write(const char *msg, int msg_len) */ cookie = console_srcu_read_lock(); for_each_console_srcu(c) { - if (!(console_srcu_read_flags(c) & CON_ENABLED)) + short flags = console_srcu_read_flags(c); + + if (!console_is_usable(c, flags, true)) continue; if (c == dbg_io_ops->cons) continue; - if (!c->write) - continue; - /* - * Set oops_in_progress to encourage the console drivers to - * disregard their internal spin locks: in the current calling - * context the risk of deadlock is a bigger problem than risks - * due to re-entering the console driver. We operate directly on - * oops_in_progress rather than using bust_spinlocks() because - * the calls bust_spinlocks() makes on exit are not appropriate - * for this calling context. - */ - ++oops_in_progress; - c->write(c, msg, msg_len); - --oops_in_progress; + + if (flags & CON_NBCON) { + struct nbcon_write_context wctxt = { }; + + /* + * Do not continue if the console is NBCON and the context + * can't be acquired. + */ + if (!nbcon_kdb_try_acquire(c, &wctxt)) + continue; + + nbcon_write_context_set_buf(&wctxt, (char *)msg, msg_len); + + c->write_atomic(c, &wctxt); + nbcon_kdb_release(&wctxt); + } else { + /* + * Set oops_in_progress to encourage the console drivers to + * disregard their internal spin locks: in the current calling + * context the risk of deadlock is a bigger problem than risks + * due to re-entering the console driver. We operate directly on + * oops_in_progress rather than using bust_spinlocks() because + * the calls bust_spinlocks() makes on exit are not appropriate + * for this calling context. + */ + ++oops_in_progress; + c->write(c, msg, msg_len); + --oops_in_progress; + } touch_nmi_watchdog(); } console_srcu_read_unlock(cookie); diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h index f72bbfa266d6..7e3128ec9336 100644 --- a/kernel/printk/internal.h +++ b/kernel/printk/internal.h @@ -3,7 +3,6 @@ * internal.h - printk internal definitions */ #include <linux/console.h> -#include <linux/percpu.h> #include <linux/types.h> #if defined(CONFIG_PRINTK) && defined(CONFIG_SYSCTL) @@ -112,47 +111,6 @@ bool nbcon_kthread_create(struct console *con); void nbcon_kthread_stop(struct console *con); void nbcon_kthreads_wake(void); -/* - * Check if the given console is currently capable and allowed to print - * records. Note that this function does not consider the current context, - * which can also play a role in deciding if @con can be used to print - * records. - */ -static inline bool console_is_usable(struct console *con, short flags, bool use_atomic) -{ - if (!(flags & CON_ENABLED)) - return false; - - if ((flags & CON_SUSPENDED)) - return false; - - if (flags & CON_NBCON) { - /* The write_atomic() callback is optional. */ - if (use_atomic && !con->write_atomic) - return false; - - /* - * For the !use_atomic case, @printk_kthreads_running is not - * checked because the write_thread() callback is also used - * via the legacy loop when the printer threads are not - * available. - */ - } else { - if (!con->write) - return false; - } - - /* - * Console drivers may assume that per-cpu resources have been - * allocated. So unless they're explicitly marked as being able to - * cope (CON_ANYTIME) don't call them until this CPU is officially up. - */ - if (!cpu_online(raw_smp_processor_id()) && !(flags & CON_ANYTIME)) - return false; - - return true; -} - /** * nbcon_kthread_wake - Wake up a console printing thread * @con: Console to operate on @@ -204,9 +162,6 @@ static inline bool nbcon_legacy_emit_next_record(struct console *con, bool *hand static inline void nbcon_kthread_wake(struct console *con) { } static inline void nbcon_kthreads_wake(void) { } -static inline bool console_is_usable(struct console *con, short flags, - bool use_atomic) { return false; } - #endif /* CONFIG_PRINTK */ extern bool have_boot_console; diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c index 3060360fb357..89c182007b20 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> @@ -252,13 +253,16 @@ 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; } @@ -853,8 +857,8 @@ out: return nbcon_context_can_proceed(ctxt, &cur); } -static void nbcon_write_context_set_buf(struct nbcon_write_context *wctxt, - char *buf, unsigned int len) +void nbcon_write_context_set_buf(struct nbcon_write_context *wctxt, + char *buf, unsigned int len) { struct nbcon_context *ctxt = &ACCESS_PRIVATE(wctxt, ctxt); struct console *con = ctxt->console; @@ -1894,3 +1898,64 @@ void nbcon_device_release(struct console *con) console_srcu_read_unlock(cookie); } EXPORT_SYMBOL_GPL(nbcon_device_release); + +/** + * nbcon_kdb_try_acquire - Try to acquire nbcon console and enter unsafe + * section + * @con: The nbcon console to acquire + * @wctxt: The nbcon write context to be used on success + * + * Context: Under console_srcu_read_lock() for emitting a single kdb message + * using the given con->write_atomic() callback. Can be called + * only when the console is usable at the moment. + * + * Return: True if the console was acquired. False otherwise. + * + * kdb emits messages on consoles registered for printk() without + * storing them into the ring buffer. It has to acquire the console + * ownerhip so that it could call con->write_atomic() callback a safe way. + * + * This function acquires the nbcon console using priority NBCON_PRIO_EMERGENCY + * and marks it unsafe for handover/takeover. + */ +bool nbcon_kdb_try_acquire(struct console *con, + struct nbcon_write_context *wctxt) +{ + struct nbcon_context *ctxt = &ACCESS_PRIVATE(wctxt, ctxt); + + memset(ctxt, 0, sizeof(*ctxt)); + ctxt->console = con; + ctxt->prio = NBCON_PRIO_EMERGENCY; + + if (!nbcon_context_try_acquire(ctxt, false)) + return false; + + if (!nbcon_context_enter_unsafe(ctxt)) + return false; + + return true; +} + +/** + * nbcon_kdb_release - Exit unsafe section and release the nbcon console + * + * @wctxt: The nbcon write context initialized by a successful + * nbcon_kdb_try_acquire() + */ +void nbcon_kdb_release(struct nbcon_write_context *wctxt) +{ + struct nbcon_context *ctxt = &ACCESS_PRIVATE(wctxt, ctxt); + + if (!nbcon_context_exit_unsafe(ctxt)) + return; + + nbcon_context_release(ctxt); + + /* + * Flush any new printk() messages added when the console was blocked. + * Only the console used by the given write context was blocked. + * The console was locked only when the write_atomic() callback + * was usable. + */ + __nbcon_atomic_flush_pending_con(ctxt->console, prb_next_reserve_seq(prb), false); +} diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 5aee9ffb16b9..ac5f38213f82 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -3331,12 +3331,10 @@ void console_unblank(void) */ cookie = console_srcu_read_lock(); for_each_console_srcu(c) { - short flags = console_srcu_read_flags(c); - - if (flags & CON_SUSPENDED) + if (!console_is_usable(c, console_srcu_read_flags(c), true)) continue; - if ((flags & CON_ENABLED) && c->unblank) { + if (c->unblank) { found_unblank = true; break; } @@ -3373,12 +3371,10 @@ void console_unblank(void) cookie = console_srcu_read_lock(); for_each_console_srcu(c) { - short flags = console_srcu_read_flags(c); - - if (flags & CON_SUSPENDED) + if (!console_is_usable(c, console_srcu_read_flags(c), true)) continue; - if ((flags & CON_ENABLED) && c->unblank) + if (c->unblank) c->unblank(); } console_srcu_read_unlock(cookie); |