diff --git a/include/linux/console.h b/include/linux/console.h index ca1ef8700e55..20cd486b76ad 100644 --- a/include/linux/console.h +++ b/include/linux/console.h @@ -243,6 +243,7 @@ struct printk_buffers; * might cause a system freeze when the console * is used later. * @pbufs: Pointer to the text buffer for this context + * @seq: The sequence number to print for this context */ struct nbcon_context { /* members set by caller */ @@ -253,6 +254,7 @@ struct nbcon_context { /* members set by acquire */ struct printk_buffers *pbufs; + u64 seq; }; /** @@ -276,6 +278,7 @@ struct nbcon_context { * @node: hlist node for the console list * * @nbcon_state: State for nbcon consoles + * @nbcon_seq: Sequence number of the next record for nbcon to print * @pbufs: Pointer to nbcon private buffer */ struct console { @@ -299,6 +302,7 @@ struct console { /* nbcon console specific members */ atomic_t __private nbcon_state; + atomic_long_t __private nbcon_seq; struct printk_buffers *pbufs; }; diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h index f6161cd75d7d..6473f5ae4a18 100644 --- a/kernel/printk/internal.h +++ b/kernel/printk/internal.h @@ -4,6 +4,7 @@ */ #include #include +#include "printk_ringbuffer.h" #if defined(CONFIG_PRINTK) && defined(CONFIG_SYSCTL) void __init printk_sysctl_init(void); @@ -42,6 +43,8 @@ enum printk_info_flags { LOG_CONT = 8, /* text is a fragment of a continuation line */ }; +extern struct printk_ringbuffer *prb; + __printf(4, 0) int vprintk_store(int facility, int level, const struct dev_printk_info *dev_info, @@ -69,6 +72,8 @@ void defer_console_output(void); u16 printk_parse_prefix(const char *text, int *level, enum printk_info_flags *flags); +u64 nbcon_seq_read(struct console *con); +void nbcon_seq_force(struct console *con, u64 seq); bool nbcon_alloc(struct console *con); void nbcon_init(struct console *con); void nbcon_free(struct console *con); @@ -88,6 +93,8 @@ void nbcon_free(struct console *con); #define printk_safe_exit_irqrestore(flags) local_irq_restore(flags) static inline bool printk_percpu_data_ready(void) { return false; } +static inline u64 nbcon_seq_read(struct console *con) { return 0; } +static inline void nbcon_seq_force(struct console *con, u64 seq) { } 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) { } diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c index 98e4be5429f0..e076096b31c0 100644 --- a/kernel/printk/nbcon.c +++ b/kernel/printk/nbcon.c @@ -140,6 +140,101 @@ static inline bool nbcon_state_try_cmpxchg(struct console *con, struct nbcon_sta return atomic_try_cmpxchg(&ACCESS_PRIVATE(con, nbcon_state), &cur->atom, new->atom); } +#ifdef CONFIG_64BIT + +#define __seq_to_nbcon_seq(seq) (seq) +#define __nbcon_seq_to_seq(seq) (seq) + +#else /* CONFIG_64BIT */ + +#define __seq_to_nbcon_seq(seq) ((u32)seq) + +static inline u64 __nbcon_seq_to_seq(u32 nbcon_seq) +{ + u64 seq; + u64 rb_next_seq; + + /* + * The provided sequence is only the lower 32 bits of the ringbuffer + * sequence. It needs to be expanded to 64bit. Get the next sequence + * number from the ringbuffer and fold it. + * + * Having a 32bit representation in the console is sufficient. + * If a console ever gets more than 2^31 records behind + * the ringbuffer then this is the least of the problems. + * + * Also the access to the ring buffer is always safe. + */ + rb_next_seq = prb_next_seq(prb); + seq = rb_next_seq - ((u32)rb_next_seq - nbcon_seq); + + return seq; +} + +#endif /* CONFIG_64BIT */ + +/** + * nbcon_seq_read - Read the current console sequence + * @con: Console to read the sequence of + * + * Return: Sequence number of the next record to print on @con. + */ +u64 nbcon_seq_read(struct console *con) +{ + unsigned long nbcon_seq = atomic_long_read(&ACCESS_PRIVATE(con, nbcon_seq)); + + return __nbcon_seq_to_seq(nbcon_seq); +} + +/** + * nbcon_seq_force - Force console sequence to a specific value + * @con: Console to work on + * @seq: Sequence number value to set + * + * Only to be used during init (before registration) or in extreme situations + * (such as panic with CONSOLE_REPLAY_ALL). + */ +void nbcon_seq_force(struct console *con, u64 seq) +{ + /* + * If the specified record no longer exists, the oldest available record + * is chosen. This is especially important on 32bit systems because only + * the lower 32 bits of the sequence number are stored. The upper 32 bits + * are derived from the sequence numbers available in the ringbuffer. + */ + u64 valid_seq = max_t(u64, seq, prb_first_valid_seq(prb)); + + atomic_long_set(&ACCESS_PRIVATE(con, nbcon_seq), __seq_to_nbcon_seq(valid_seq)); + + /* Clear con->seq since nbcon consoles use con->nbcon_seq instead. */ + con->seq = 0; +} + +/** + * nbcon_seq_try_update - Try to update the console sequence number + * @ctxt: Pointer to an acquire context that contains + * all information about the acquire mode + * @new_seq: The new sequence number to set + * + * @ctxt->seq is updated to the new value of @con::nbcon_seq (expanded to + * the 64bit value). This could be a different value than @new_seq if + * nbcon_seq_force() was used or the current context no longer owns the + * console. In the later case, it will stop printing anyway. + */ +__maybe_unused +static void nbcon_seq_try_update(struct nbcon_context *ctxt, u64 new_seq) +{ + unsigned long nbcon_seq = __seq_to_nbcon_seq(ctxt->seq); + struct console *con = ctxt->console; + + if (atomic_long_try_cmpxchg(&ACCESS_PRIVATE(con, nbcon_seq), &nbcon_seq, + __seq_to_nbcon_seq(new_seq))) { + ctxt->seq = new_seq; + } else { + ctxt->seq = nbcon_seq_read(con); + } +} + /** * nbcon_context_try_acquire_direct - Try to acquire directly * @ctxt: The context of the caller @@ -510,6 +605,9 @@ out: else ctxt->pbufs = con->pbufs; + /* Set the record sequence for this context to print. */ + ctxt->seq = nbcon_seq_read(ctxt->console); + return true; } @@ -722,6 +820,8 @@ bool nbcon_alloc(struct console *con) * * nbcon_alloc() *must* be called and succeed before this function * is called. + * + * This function expects that the legacy @con->seq has been set. */ void nbcon_init(struct console *con) { @@ -730,6 +830,7 @@ void nbcon_init(struct console *con) /* nbcon_alloc() must have been called and successful! */ BUG_ON(!con->pbufs); + nbcon_seq_force(con, con->seq); nbcon_state_set(con, &state); } diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 1c9720acd960..77857d2118ca 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -494,7 +494,7 @@ _DEFINE_PRINTKRB(printk_rb_static, CONFIG_LOG_BUF_SHIFT - PRB_AVGBITS, static struct printk_ringbuffer printk_rb_dynamic; -static struct printk_ringbuffer *prb = &printk_rb_static; +struct printk_ringbuffer *prb = &printk_rb_static; /* * We cannot access per-CPU data (e.g. per-CPU flush irq_work) before @@ -3168,6 +3168,7 @@ void console_flush_on_panic(enum con_flush_mode mode) if (mode == CONSOLE_REPLAY_ALL) { struct console *c; + short flags; int cookie; u64 seq; @@ -3175,11 +3176,17 @@ void console_flush_on_panic(enum con_flush_mode mode) cookie = console_srcu_read_lock(); for_each_console_srcu(c) { - /* - * This is an unsynchronized assignment, but the - * kernel is in "hope and pray" mode anyway. - */ - c->seq = seq; + flags = console_srcu_read_flags(c); + + if (flags & CON_NBCON) { + nbcon_seq_force(c, seq); + } else { + /* + * This is an unsynchronized assignment. On + * panic legacy consoles are only best effort. + */ + c->seq = seq; + } } console_srcu_read_unlock(cookie); } @@ -3750,6 +3757,7 @@ static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progre struct console *c; u64 last_diff = 0; u64 printk_seq; + short flags; int cookie; u64 diff; u64 seq; @@ -3771,6 +3779,9 @@ static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progre for_each_console_srcu(c) { if (con && con != c) continue; + + flags = console_srcu_read_flags(c); + /* * If consoles are not usable, it cannot be expected * that they make forward progress, so only increment @@ -3778,7 +3789,13 @@ static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progre */ if (!console_is_usable(c)) continue; - printk_seq = c->seq; + + if (flags & CON_NBCON) { + printk_seq = nbcon_seq_read(c); + } else { + printk_seq = c->seq; + } + if (printk_seq < seq) diff += seq - printk_seq; }