diff options
Diffstat (limited to '')
| -rw-r--r-- | kernel/printk/internal.h | 1 | ||||
| -rw-r--r-- | kernel/printk/nbcon.c | 41 | ||||
| -rw-r--r-- | kernel/printk/printk.c | 101 | ||||
| -rw-r--r-- | kernel/printk/printk_ringbuffer.c | 315 | ||||
| -rw-r--r-- | kernel/printk/printk_ringbuffer.h | 38 |
5 files changed, 384 insertions, 112 deletions
diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h index 6c2afee5ef..ac2d9750e5 100644 --- a/kernel/printk/internal.h +++ b/kernel/printk/internal.h @@ -130,6 +130,7 @@ struct printk_message { }; bool other_cpu_in_panic(void); +bool this_cpu_in_panic(void); bool printk_get_next_message(struct printk_message *pmsg, u64 seq, bool is_extended, bool may_supress); diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c index b96077152f..c8093bcc01 100644 --- a/kernel/printk/nbcon.c +++ b/kernel/printk/nbcon.c @@ -140,39 +140,6 @@ 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 @@ -183,7 +150,7 @@ 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); + return __ulseq_to_u64seq(prb, nbcon_seq); } /** @@ -204,7 +171,7 @@ void nbcon_seq_force(struct console *con, u64 seq) */ 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)); + atomic_long_set(&ACCESS_PRIVATE(con, nbcon_seq), __u64seq_to_ulseq(valid_seq)); /* Clear con->seq since nbcon consoles use con->nbcon_seq instead. */ con->seq = 0; @@ -223,11 +190,11 @@ void nbcon_seq_force(struct console *con, u64 seq) */ static void nbcon_seq_try_update(struct nbcon_context *ctxt, u64 new_seq) { - unsigned long nbcon_seq = __seq_to_nbcon_seq(ctxt->seq); + unsigned long nbcon_seq = __u64seq_to_ulseq(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))) { + __u64seq_to_ulseq(new_seq))) { ctxt->seq = new_seq; } else { ctxt->seq = nbcon_seq_read(con); diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index f2444b581e..7a835b277e 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -347,6 +347,29 @@ static bool panic_in_progress(void) return unlikely(atomic_read(&panic_cpu) != PANIC_CPU_INVALID); } +/* Return true if a panic is in progress on the current CPU. */ +bool this_cpu_in_panic(void) +{ + /* + * We can use raw_smp_processor_id() here because it is impossible for + * the task to be migrated to the panic_cpu, or away from it. If + * panic_cpu has already been set, and we're not currently executing on + * that CPU, then we never will be. + */ + return unlikely(atomic_read(&panic_cpu) == raw_smp_processor_id()); +} + +/* + * Return true if a panic is in progress on a remote CPU. + * + * On true, the local CPU should immediately release any printing resources + * that may be needed by the panic CPU. + */ +bool other_cpu_in_panic(void) +{ + return (panic_in_progress() && !this_cpu_in_panic()); +} + /* * This is used for debugging the mess that is the VT code by * keeping track if we have the console semaphore held. It's @@ -1846,10 +1869,23 @@ static bool console_waiter; */ static void console_lock_spinning_enable(void) { + /* + * Do not use spinning in panic(). The panic CPU wants to keep the lock. + * Non-panic CPUs abandon the flush anyway. + * + * Just keep the lockdep annotation. The panic-CPU should avoid + * taking console_owner_lock because it might cause a deadlock. + * This looks like the easiest way how to prevent false lockdep + * reports without handling races a lockless way. + */ + if (panic_in_progress()) + goto lockdep; + raw_spin_lock(&console_owner_lock); console_owner = current; raw_spin_unlock(&console_owner_lock); +lockdep: /* The waiter may spin on us after setting console_owner */ spin_acquire(&console_owner_dep_map, 0, 0, _THIS_IP_); } @@ -1874,6 +1910,22 @@ static int console_lock_spinning_disable_and_check(int cookie) { int waiter; + /* + * Ignore spinning waiters during panic() because they might get stopped + * or blocked at any time, + * + * It is safe because nobody is allowed to start spinning during panic + * in the first place. If there has been a waiter then non panic CPUs + * might stay spinning. They would get stopped anyway. The panic context + * will never start spinning and an interrupted spin on panic CPU will + * never continue. + */ + if (panic_in_progress()) { + /* Keep lockdep happy. */ + spin_release(&console_owner_dep_map, _THIS_IP_); + return 0; + } + raw_spin_lock(&console_owner_lock); waiter = READ_ONCE(console_waiter); console_owner = NULL; @@ -1974,6 +2026,12 @@ static int console_trylock_spinning(void) */ mutex_acquire(&console_lock_dep_map, 0, 1, _THIS_IP_); + /* + * Update @console_may_schedule for trylock because the previous + * owner may have been schedulable. + */ + console_may_schedule = 0; + return 1; } @@ -2601,26 +2659,6 @@ static int console_cpu_notify(unsigned int cpu) return 0; } -/* - * Return true if a panic is in progress on a remote CPU. - * - * On true, the local CPU should immediately release any printing resources - * that may be needed by the panic CPU. - */ -bool other_cpu_in_panic(void) -{ - if (!panic_in_progress()) - return false; - - /* - * We can use raw_smp_processor_id() here because it is impossible for - * the task to be migrated to the panic_cpu, or away from it. If - * panic_cpu has already been set, and we're not currently executing on - * that CPU, then we never will be. - */ - return atomic_read(&panic_cpu) != raw_smp_processor_id(); -} - /** * console_lock - block the console subsystem from printing * @@ -3263,6 +3301,21 @@ static int __init keep_bootcon_setup(char *str) early_param("keep_bootcon", keep_bootcon_setup); +static int console_call_setup(struct console *newcon, char *options) +{ + int err; + + if (!newcon->setup) + return 0; + + /* Synchronize with possible boot console. */ + console_lock(); + err = newcon->setup(newcon, options); + console_unlock(); + + return err; +} + /* * This is called by register_console() to try to match * the newly registered console with any of the ones selected @@ -3298,8 +3351,8 @@ static int try_enable_preferred_console(struct console *newcon, if (_braille_register_console(newcon, c)) return 0; - if (newcon->setup && - (err = newcon->setup(newcon, c->options)) != 0) + err = console_call_setup(newcon, c->options); + if (err) return err; } newcon->flags |= CON_ENABLED; @@ -3325,7 +3378,7 @@ static void try_enable_default_console(struct console *newcon) if (newcon->index < 0) newcon->index = 0; - if (newcon->setup && newcon->setup(newcon, NULL) != 0) + if (console_call_setup(newcon, NULL) != 0) return; newcon->flags |= CON_ENABLED; @@ -3761,7 +3814,7 @@ static bool __pr_flush(struct console *con, int timeout_ms, bool reset_on_progre might_sleep(); - seq = prb_next_seq(prb); + seq = prb_next_reserve_seq(prb); /* Flush the consoles so that records up to @seq are printed. */ console_lock(); diff --git a/kernel/printk/printk_ringbuffer.c b/kernel/printk/printk_ringbuffer.c index fde338606c..f5a8bb606f 100644 --- a/kernel/printk/printk_ringbuffer.c +++ b/kernel/printk/printk_ringbuffer.c @@ -6,6 +6,7 @@ #include <linux/errno.h> #include <linux/bug.h> #include "printk_ringbuffer.h" +#include "internal.h" /** * DOC: printk_ringbuffer overview @@ -303,6 +304,9 @@ * * desc_push_tail:B / desc_reserve:D * set descriptor reusable (state), then push descriptor tail (id) + * + * desc_update_last_finalized:A / desc_last_finalized_seq:A + * store finalized record, then set new highest finalized sequence number */ #define DATA_SIZE(data_ring) _DATA_SIZE((data_ring)->size_bits) @@ -1442,19 +1446,117 @@ fail_reopen: } /* + * @last_finalized_seq value guarantees that all records up to and including + * this sequence number are finalized and can be read. The only exception are + * too old records which have already been overwritten. + * + * It is also guaranteed that @last_finalized_seq only increases. + * + * Be aware that finalized records following non-finalized records are not + * reported because they are not yet available to the reader. For example, + * a new record stored via printk() will not be available to a printer if + * it follows a record that has not been finalized yet. However, once that + * non-finalized record becomes finalized, @last_finalized_seq will be + * appropriately updated and the full set of finalized records will be + * available to the printer. And since each printk() caller will either + * directly print or trigger deferred printing of all available unprinted + * records, all printk() messages will get printed. + */ +static u64 desc_last_finalized_seq(struct printk_ringbuffer *rb) +{ + struct prb_desc_ring *desc_ring = &rb->desc_ring; + unsigned long ulseq; + + /* + * Guarantee the sequence number is loaded before loading the + * associated record in order to guarantee that the record can be + * seen by this CPU. This pairs with desc_update_last_finalized:A. + */ + ulseq = atomic_long_read_acquire(&desc_ring->last_finalized_seq + ); /* LMM(desc_last_finalized_seq:A) */ + + return __ulseq_to_u64seq(rb, ulseq); +} + +static bool _prb_read_valid(struct printk_ringbuffer *rb, u64 *seq, + struct printk_record *r, unsigned int *line_count); + +/* + * Check if there are records directly following @last_finalized_seq that are + * finalized. If so, update @last_finalized_seq to the latest of these + * records. It is not allowed to skip over records that are not yet finalized. + */ +static void desc_update_last_finalized(struct printk_ringbuffer *rb) +{ + struct prb_desc_ring *desc_ring = &rb->desc_ring; + u64 old_seq = desc_last_finalized_seq(rb); + unsigned long oldval; + unsigned long newval; + u64 finalized_seq; + u64 try_seq; + +try_again: + finalized_seq = old_seq; + try_seq = finalized_seq + 1; + + /* Try to find later finalized records. */ + while (_prb_read_valid(rb, &try_seq, NULL, NULL)) { + finalized_seq = try_seq; + try_seq++; + } + + /* No update needed if no later finalized record was found. */ + if (finalized_seq == old_seq) + return; + + oldval = __u64seq_to_ulseq(old_seq); + newval = __u64seq_to_ulseq(finalized_seq); + + /* + * Set the sequence number of a later finalized record that has been + * seen. + * + * Guarantee the record data is visible to other CPUs before storing + * its sequence number. This pairs with desc_last_finalized_seq:A. + * + * Memory barrier involvement: + * + * If desc_last_finalized_seq:A reads from + * desc_update_last_finalized:A, then desc_read:A reads from + * _prb_commit:B. + * + * Relies on: + * + * RELEASE from _prb_commit:B to desc_update_last_finalized:A + * matching + * ACQUIRE from desc_last_finalized_seq:A to desc_read:A + * + * Note: _prb_commit:B and desc_update_last_finalized:A can be + * different CPUs. However, the desc_update_last_finalized:A + * CPU (which performs the release) must have previously seen + * _prb_commit:B. + */ + if (!atomic_long_try_cmpxchg_release(&desc_ring->last_finalized_seq, + &oldval, newval)) { /* LMM(desc_update_last_finalized:A) */ + old_seq = __ulseq_to_u64seq(rb, oldval); + goto try_again; + } +} + +/* * Attempt to finalize a specified descriptor. If this fails, the descriptor * is either already final or it will finalize itself when the writer commits. */ -static void desc_make_final(struct prb_desc_ring *desc_ring, unsigned long id) +static void desc_make_final(struct printk_ringbuffer *rb, unsigned long id) { + struct prb_desc_ring *desc_ring = &rb->desc_ring; unsigned long prev_state_val = DESC_SV(id, desc_committed); struct prb_desc *d = to_desc(desc_ring, id); - atomic_long_cmpxchg_relaxed(&d->state_var, prev_state_val, - DESC_SV(id, desc_finalized)); /* LMM(desc_make_final:A) */ - - /* Best effort to remember the last finalized @id. */ - atomic_long_set(&desc_ring->last_finalized_id, id); + if (atomic_long_try_cmpxchg_relaxed(&d->state_var, &prev_state_val, + DESC_SV(id, desc_finalized))) { /* LMM(desc_make_final:A) */ + desc_update_last_finalized(rb); + } } /** @@ -1550,7 +1652,7 @@ bool prb_reserve(struct prb_reserved_entry *e, struct printk_ringbuffer *rb, * readers. (For seq==0 there is no previous descriptor.) */ if (info->seq > 0) - desc_make_final(desc_ring, DESC_ID(id - 1)); + desc_make_final(rb, DESC_ID(id - 1)); r->text_buf = data_alloc(rb, r->text_buf_size, &d->text_blk_lpos, id); /* If text data allocation fails, a data-less record is committed. */ @@ -1643,7 +1745,7 @@ void prb_commit(struct prb_reserved_entry *e) */ head_id = atomic_long_read(&desc_ring->head_id); /* LMM(prb_commit:A) */ if (head_id != e->id) - desc_make_final(desc_ring, e->id); + desc_make_final(e->rb, e->id); } /** @@ -1663,12 +1765,9 @@ void prb_commit(struct prb_reserved_entry *e) */ void prb_final_commit(struct prb_reserved_entry *e) { - struct prb_desc_ring *desc_ring = &e->rb->desc_ring; - _prb_commit(e, desc_finalized); - /* Best effort to remember the last finalized @id. */ - atomic_long_set(&desc_ring->last_finalized_id, e->id); + desc_update_last_finalized(e->rb); } /* @@ -1832,7 +1931,7 @@ static int prb_read(struct printk_ringbuffer *rb, u64 seq, } /* Get the sequence number of the tail descriptor. */ -static u64 prb_first_seq(struct printk_ringbuffer *rb) +u64 prb_first_seq(struct printk_ringbuffer *rb) { struct prb_desc_ring *desc_ring = &rb->desc_ring; enum desc_state d_state; @@ -1875,12 +1974,123 @@ static u64 prb_first_seq(struct printk_ringbuffer *rb) return seq; } +/** + * prb_next_reserve_seq() - Get the sequence number after the most recently + * reserved record. + * + * @rb: The ringbuffer to get the sequence number from. + * + * This is the public function available to readers to see what sequence + * number will be assigned to the next reserved record. + * + * Note that depending on the situation, this value can be equal to or + * higher than the sequence number returned by prb_next_seq(). + * + * Context: Any context. + * Return: The sequence number that will be assigned to the next record + * reserved. + */ +u64 prb_next_reserve_seq(struct printk_ringbuffer *rb) +{ + struct prb_desc_ring *desc_ring = &rb->desc_ring; + unsigned long last_finalized_id; + atomic_long_t *state_var; + u64 last_finalized_seq; + unsigned long head_id; + struct prb_desc desc; + unsigned long diff; + struct prb_desc *d; + int err; + + /* + * It may not be possible to read a sequence number for @head_id. + * So the ID of @last_finailzed_seq is used to calculate what the + * sequence number of @head_id will be. + */ + +try_again: + last_finalized_seq = desc_last_finalized_seq(rb); + + /* + * @head_id is loaded after @last_finalized_seq to ensure that + * it points to the record with @last_finalized_seq or newer. + * + * Memory barrier involvement: + * + * If desc_last_finalized_seq:A reads from + * desc_update_last_finalized:A, then + * prb_next_reserve_seq:A reads from desc_reserve:D. + * + * Relies on: + * + * RELEASE from desc_reserve:D to desc_update_last_finalized:A + * matching + * ACQUIRE from desc_last_finalized_seq:A to prb_next_reserve_seq:A + * + * Note: desc_reserve:D and desc_update_last_finalized:A can be + * different CPUs. However, the desc_update_last_finalized:A CPU + * (which performs the release) must have previously seen + * desc_read:C, which implies desc_reserve:D can be seen. + */ + head_id = atomic_long_read(&desc_ring->head_id); /* LMM(prb_next_reserve_seq:A) */ + + d = to_desc(desc_ring, last_finalized_seq); + state_var = &d->state_var; + + /* Extract the ID, used to specify the descriptor to read. */ + last_finalized_id = DESC_ID(atomic_long_read(state_var)); + + /* Ensure @last_finalized_id is correct. */ + err = desc_read_finalized_seq(desc_ring, last_finalized_id, last_finalized_seq, &desc); + + if (err == -EINVAL) { + if (last_finalized_seq == 0) { + /* + * No record has been finalized or even reserved yet. + * + * The @head_id is initialized such that the first + * increment will yield the first record (seq=0). + * Handle it separately to avoid a negative @diff + * below. + */ + if (head_id == DESC0_ID(desc_ring->count_bits)) + return 0; + + /* + * One or more descriptors are already reserved. Use + * the descriptor ID of the first one (@seq=0) for + * the @diff below. + */ + last_finalized_id = DESC0_ID(desc_ring->count_bits) + 1; + } else { + /* Record must have been overwritten. Try again. */ + goto try_again; + } + } + + /* Diff of known descriptor IDs to compute related sequence numbers. */ + diff = head_id - last_finalized_id; + + /* + * @head_id points to the most recently reserved record, but this + * function returns the sequence number that will be assigned to the + * next (not yet reserved) record. Thus +1 is needed. + */ + return (last_finalized_seq + diff + 1); +} + /* - * Non-blocking read of a record. Updates @seq to the last finalized record - * (which may have no data available). + * Non-blocking read of a record. + * + * On success @seq is updated to the record that was read and (if provided) + * @r and @line_count will contain the read/calculated data. + * + * On failure @seq is updated to a record that is not yet available to the + * reader, but it will be the next record available to the reader. * - * See the description of prb_read_valid() and prb_read_valid_info() - * for details. + * Note: When the current CPU is in panic, this function will skip over any + * non-existent/non-finalized records in order to allow the panic CPU + * to print any and all records that have been finalized. */ static bool _prb_read_valid(struct printk_ringbuffer *rb, u64 *seq, struct printk_record *r, unsigned int *line_count) @@ -1899,12 +2109,32 @@ static bool _prb_read_valid(struct printk_ringbuffer *rb, u64 *seq, *seq = tail_seq; } else if (err == -ENOENT) { - /* Record exists, but no data available. Skip. */ + /* Record exists, but the data was lost. Skip. */ (*seq)++; } else { - /* Non-existent/non-finalized record. Must stop. */ - return false; + /* + * Non-existent/non-finalized record. Must stop. + * + * For panic situations it cannot be expected that + * non-finalized records will become finalized. But + * there may be other finalized records beyond that + * need to be printed for a panic situation. If this + * is the panic CPU, skip this + * non-existent/non-finalized record unless it is + * at or beyond the head, in which case it is not + * possible to continue. + * + * Note that new messages printed on panic CPU are + * finalized when we are here. The only exception + * might be the last message without trailing newline. + * But it would have the sequence number returned + * by "prb_next_reserve_seq() - 1". + */ + if (this_cpu_in_panic() && ((*seq + 1) < prb_next_reserve_seq(rb))) + (*seq)++; + else + return false; } } @@ -1932,7 +2162,7 @@ static bool _prb_read_valid(struct printk_ringbuffer *rb, u64 *seq, * On success, the reader must check r->info.seq to see which record was * actually read. This allows the reader to detect dropped records. * - * Failure means @seq refers to a not yet written record. + * Failure means @seq refers to a record not yet available to the reader. */ bool prb_read_valid(struct printk_ringbuffer *rb, u64 seq, struct printk_record *r) @@ -1962,7 +2192,7 @@ bool prb_read_valid(struct printk_ringbuffer *rb, u64 seq, * On success, the reader must check info->seq to see which record meta data * was actually read. This allows the reader to detect dropped records. * - * Failure means @seq refers to a not yet written record. + * Failure means @seq refers to a record not yet available to the reader. */ bool prb_read_valid_info(struct printk_ringbuffer *rb, u64 seq, struct printk_info *info, unsigned int *line_count) @@ -2008,7 +2238,9 @@ u64 prb_first_valid_seq(struct printk_ringbuffer *rb) * newest sequence number available to readers will be. * * This provides readers a sequence number to jump to if all currently - * available records should be skipped. + * available records should be skipped. It is guaranteed that all records + * previous to the returned value have been finalized and are (or were) + * available to the reader. * * Context: Any context. * Return: The sequence number of the next newest (not yet available) record @@ -2016,34 +2248,19 @@ u64 prb_first_valid_seq(struct printk_ringbuffer *rb) */ u64 prb_next_seq(struct printk_ringbuffer *rb) { - struct prb_desc_ring *desc_ring = &rb->desc_ring; - enum desc_state d_state; - unsigned long id; u64 seq; - /* Check if the cached @id still points to a valid @seq. */ - id = atomic_long_read(&desc_ring->last_finalized_id); - d_state = desc_read(desc_ring, id, NULL, &seq, NULL); + seq = desc_last_finalized_seq(rb); - if (d_state == desc_finalized || d_state == desc_reusable) { - /* - * Begin searching after the last finalized record. - * - * On 0, the search must begin at 0 because of hack#2 - * of the bootstrapping phase it is not known if a - * record at index 0 exists. - */ - if (seq != 0) - seq++; - } else { - /* - * The information about the last finalized sequence number - * has gone. It should happen only when there is a flood of - * new messages and the ringbuffer is rapidly recycled. - * Give up and start from the beginning. - */ - seq = 0; - } + /* + * Begin searching after the last finalized record. + * + * On 0, the search must begin at 0 because of hack#2 + * of the bootstrapping phase it is not known if a + * record at index 0 exists. + */ + if (seq != 0) + seq++; /* * The information about the last finalized @seq might be inaccurate. @@ -2085,7 +2302,7 @@ void prb_init(struct printk_ringbuffer *rb, rb->desc_ring.infos = infos; atomic_long_set(&rb->desc_ring.head_id, DESC0_ID(descbits)); atomic_long_set(&rb->desc_ring.tail_id, DESC0_ID(descbits)); - atomic_long_set(&rb->desc_ring.last_finalized_id, DESC0_ID(descbits)); + atomic_long_set(&rb->desc_ring.last_finalized_seq, 0); rb->text_data_ring.size_bits = textbits; rb->text_data_ring.data = text_buf; diff --git a/kernel/printk/printk_ringbuffer.h b/kernel/printk/printk_ringbuffer.h index 18cd25e489..cb887489d0 100644 --- a/kernel/printk/printk_ringbuffer.h +++ b/kernel/printk/printk_ringbuffer.h @@ -75,7 +75,7 @@ struct prb_desc_ring { struct printk_info *infos; atomic_long_t head_id; atomic_long_t tail_id; - atomic_long_t last_finalized_id; + atomic_long_t last_finalized_seq; }; /* @@ -259,7 +259,7 @@ static struct printk_ringbuffer name = { \ .infos = &_##name##_infos[0], \ .head_id = ATOMIC_INIT(DESC0_ID(descbits)), \ .tail_id = ATOMIC_INIT(DESC0_ID(descbits)), \ - .last_finalized_id = ATOMIC_INIT(DESC0_ID(descbits)), \ + .last_finalized_seq = ATOMIC_INIT(0), \ }, \ .text_data_ring = { \ .size_bits = (avgtextbits) + (descbits), \ @@ -378,7 +378,41 @@ bool prb_read_valid(struct printk_ringbuffer *rb, u64 seq, bool prb_read_valid_info(struct printk_ringbuffer *rb, u64 seq, struct printk_info *info, unsigned int *line_count); +u64 prb_first_seq(struct printk_ringbuffer *rb); u64 prb_first_valid_seq(struct printk_ringbuffer *rb); u64 prb_next_seq(struct printk_ringbuffer *rb); +u64 prb_next_reserve_seq(struct printk_ringbuffer *rb); + +#ifdef CONFIG_64BIT + +#define __u64seq_to_ulseq(u64seq) (u64seq) +#define __ulseq_to_u64seq(rb, ulseq) (ulseq) + +#else /* CONFIG_64BIT */ + +#define __u64seq_to_ulseq(u64seq) ((u32)u64seq) + +static inline u64 __ulseq_to_u64seq(struct printk_ringbuffer *rb, u32 ulseq) +{ + u64 rb_first_seq = prb_first_seq(rb); + u64 seq; + + /* + * The provided sequence is only the lower 32 bits of the ringbuffer + * sequence. It needs to be expanded to 64bit. Get the first 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. + */ + seq = rb_first_seq - (s32)((u32)rb_first_seq - ulseq); + + return seq; +} + +#endif /* CONFIG_64BIT */ #endif /* _KERNEL_PRINTK_RINGBUFFER_H */ |