diff options
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/printk/printk_ringbuffer.c | 525 | ||||
| -rw-r--r-- | kernel/printk/printk_ringbuffer.h | 6 |
2 files changed, 476 insertions, 55 deletions
diff --git a/kernel/printk/printk_ringbuffer.c b/kernel/printk/printk_ringbuffer.c index c0d31185ccbf..f4e2e9890e0f 100644 --- a/kernel/printk/printk_ringbuffer.c +++ b/kernel/printk/printk_ringbuffer.c @@ -46,20 +46,26 @@ * into a single descriptor field named @state_var, allowing ID and state to * be synchronously and atomically updated. * - * Descriptors have three states: + * Descriptors have four states: * * reserved * A writer is modifying the record. * * committed - * The record and all its data are complete and available for reading. + * The record and all its data are written. A writer can reopen the + * descriptor (transitioning it back to reserved), but in the committed + * state the data is consistent. + * + * finalized + * The record and all its data are complete and available for reading. A + * writer cannot reopen the descriptor. * * reusable * The record exists, but its text and/or dictionary data may no longer * be available. * * Querying the @state_var of a record requires providing the ID of the - * descriptor to query. This can yield a possible fourth (pseudo) state: + * descriptor to query. This can yield a possible fifth (pseudo) state: * * miss * The descriptor being queried has an unexpected ID. @@ -79,6 +85,28 @@ * committed or reusable queried state. This makes it possible that a valid * sequence number of the tail is always available. * + * Descriptor Finalization + * ~~~~~~~~~~~~~~~~~~~~~~~ + * When a writer calls the commit function prb_commit(), record data is + * fully stored and is consistent within the ringbuffer. However, a writer can + * reopen that record, claiming exclusive access (as with prb_reserve()), and + * modify that record. When finished, the writer must again commit the record. + * + * In order for a record to be made available to readers (and also become + * recyclable for writers), it must be finalized. A finalized record cannot be + * reopened and can never become "unfinalized". Record finalization can occur + * in three different scenarios: + * + * 1) A writer can simultaneously commit and finalize its record by calling + * prb_final_commit() instead of prb_commit(). + * + * 2) When a new record is reserved and the previous record has been + * committed via prb_commit(), that previous record is automatically + * finalized. + * + * 3) When a record is committed via prb_commit() and a newer record + * already exists, the record being committed is automatically finalized. + * * Data Rings * ~~~~~~~~~~ * The two data rings (text and dictionary) function identically. They exist @@ -97,7 +125,7 @@ * are met: * * 1) The descriptor associated with the data block is in the committed - * queried state. + * or finalized queried state. * * 2) The blk_lpos struct within the descriptor associated with the data * block references back to the same data block. @@ -156,9 +184,38 @@ * * r.info->ts_nsec = local_clock(); * + * prb_final_commit(&e); + * } + * + * Note that additional writer functions are available to extend a record + * after it has been committed but not yet finalized. This can be done as + * long as no new records have been reserved and the caller is the same. + * + * Sample writer code (record extending):: + * + * // alternate rest of previous example + * r.info->ts_nsec = local_clock(); + * r.info->text_len = strlen(textstr); + * r.info->caller_id = printk_caller_id(); + * + * // commit the record (but do not finalize yet) * prb_commit(&e); * } * + * ... + * + * // specify additional 5 bytes text space to extend + * prb_rec_init_wr(&r, 5, 0); + * + * if (prb_reserve_in_last(&e, &test_rb, &r, printk_caller_id())) { + * snprintf(&r.text_buf[r.info->text_len], + * r.text_buf_size - r.info->text_len, "hello"); + * + * r.info->text_len += 5; + * + * prb_final_commit(&e); + * } + * * Sample reader code:: * * struct printk_info info; @@ -236,15 +293,21 @@ * desc_reserve:F / desc_read:D * set new descriptor id and reserved (state), then allow writer changes * - * data_alloc:A / desc_read:D + * data_alloc:A (or data_realloc:A) / desc_read:D * set old descriptor reusable (state), then modify new data block area * - * data_alloc:A / data_push_tail:B + * data_alloc:A (or data_realloc:A) / data_push_tail:B * push data tail (lpos), then modify new data block area * - * prb_commit:B / desc_read:B + * _prb_commit:B / desc_read:B * store writer changes, then set new descriptor committed (state) * + * desc_reopen_last:A / _prb_commit:B + * set descriptor reserved (state), then read descriptor data + * + * _prb_commit:B / desc_reserve:D + * set new descriptor committed (state), then check descriptor head (id) + * * data_push_tail:D / data_push_tail:A * set descriptor reusable (state), then push data tail (lpos) * @@ -386,16 +449,16 @@ static enum desc_state desc_read(struct prb_desc_ring *desc_ring, /* * Guarantee the state is loaded before copying the descriptor * content. This avoids copying obsolete descriptor content that might - * not apply to the descriptor state. This pairs with prb_commit:B. + * not apply to the descriptor state. This pairs with _prb_commit:B. * * Memory barrier involvement: * - * If desc_read:A reads from prb_commit:B, then desc_read:C reads - * from prb_commit:A. + * If desc_read:A reads from _prb_commit:B, then desc_read:C reads + * from _prb_commit:A. * * Relies on: * - * WMB from prb_commit:A to prb_commit:B + * WMB from _prb_commit:A to _prb_commit:B * matching * RMB from desc_read:A to desc_read:C */ @@ -431,7 +494,8 @@ static enum desc_state desc_read(struct prb_desc_ring *desc_ring, * * 2. Guarantee the record data is loaded before re-checking the * state. This avoids reading an obsolete descriptor state that may - * not apply to the copied data. This pairs with data_alloc:A. + * not apply to the copied data. This pairs with data_alloc:A and + * data_realloc:A. * * Memory barrier involvement: * @@ -463,19 +527,19 @@ out: } /* - * Take a specified descriptor out of the committed state by attempting - * the transition from committed to reusable. Either this context or some + * Take a specified descriptor out of the finalized state by attempting + * the transition from finalized to reusable. Either this context or some * other context will have been successful. */ static void desc_make_reusable(struct prb_desc_ring *desc_ring, unsigned long id) { - unsigned long val_committed = DESC_SV(id, desc_committed); + unsigned long val_finalized = DESC_SV(id, desc_finalized); unsigned long val_reusable = DESC_SV(id, desc_reusable); struct prb_desc *desc = to_desc(desc_ring, id); atomic_long_t *state_var = &desc->state_var; - atomic_long_cmpxchg_relaxed(state_var, val_committed, + atomic_long_cmpxchg_relaxed(state_var, val_finalized, val_reusable); /* LMM(desc_make_reusable:A) */ } @@ -484,7 +548,7 @@ static void desc_make_reusable(struct prb_desc_ring *desc_ring, * data block from @lpos_begin until @lpos_end into the reusable state. * * If there is any problem making the associated descriptor reusable, either - * the descriptor has not yet been committed or another writer context has + * the descriptor has not yet been finalized or another writer context has * already pushed the tail lpos past the problematic data block. Regardless, * on error the caller can re-load the tail lpos to determine the situation. */ @@ -528,10 +592,10 @@ static bool data_make_reusable(struct printk_ringbuffer *rb, switch (d_state) { case desc_miss: - return false; case desc_reserved: - return false; case desc_committed: + return false; + case desc_finalized: /* * This data block is invalid if the descriptor * does not point back to it. @@ -616,7 +680,7 @@ static bool data_push_tail(struct printk_ringbuffer *rb, * data_make_reusable() may be due to a newly * recycled data area causing the tail lpos to * have been previously pushed. This pairs with - * data_alloc:A. + * data_alloc:A and data_realloc:A. * * Memory barrier involvement: * @@ -729,8 +793,9 @@ static bool desc_push_tail(struct printk_ringbuffer *rb, */ return true; case desc_reserved: - return false; case desc_committed: + return false; + case desc_finalized: desc_make_reusable(desc_ring, tail_id); break; case desc_reusable: @@ -751,7 +816,7 @@ static bool desc_push_tail(struct printk_ringbuffer *rb, /* * Check the next descriptor after @tail_id before pushing the tail - * to it because the tail must always be in a committed or reusable + * to it because the tail must always be in a finalized or reusable * state. The implementation of prb_first_seq() relies on this. * * A successful read implies that the next descriptor is less than or @@ -760,7 +825,7 @@ static bool desc_push_tail(struct printk_ringbuffer *rb, */ d_state = desc_read(desc_ring, DESC_ID(tail_id + 1), &desc); /* LMM(desc_push_tail:A) */ - if (d_state == desc_committed || d_state == desc_reusable) { + if (d_state == desc_finalized || d_state == desc_reusable) { /* * Guarantee any descriptor states that have transitioned to * reusable are stored before pushing the tail ID. This allows @@ -895,6 +960,10 @@ static bool desc_reserve(struct printk_ringbuffer *rb, unsigned long *id_out) * another CPU may have pushed the tail ID. This pairs * with desc_push_tail:C and this also pairs with * prb_first_seq:C. + * + * 5. Guarantee the head ID is stored before trying to + * finalize the previous descriptor. This pairs with + * _prb_commit:B. */ } while (!atomic_long_try_cmpxchg(&desc_ring->head_id, &head_id, id)); /* LMM(desc_reserve:D) */ @@ -1024,6 +1093,84 @@ static char *data_alloc(struct printk_ringbuffer *rb, return &blk->data[0]; } +/* + * Try to resize an existing data block associated with the descriptor + * specified by @id. If the resized data block should become wrapped, it + * copies the old data to the new data block. If @size yields a data block + * with the same or less size, the data block is left as is. + * + * Fail if this is not the last allocated data block or if there is not + * enough space or it is not possible make enough space. + * + * Return a pointer to the beginning of the entire data buffer or NULL on + * failure. + */ +static char *data_realloc(struct printk_ringbuffer *rb, + struct prb_data_ring *data_ring, unsigned int size, + struct prb_data_blk_lpos *blk_lpos, unsigned long id) +{ + struct prb_data_block *blk; + unsigned long head_lpos; + unsigned long next_lpos; + bool wrapped; + + /* Reallocation only works if @blk_lpos is the newest data block. */ + head_lpos = atomic_long_read(&data_ring->head_lpos); + if (head_lpos != blk_lpos->next) + return NULL; + + /* Keep track if @blk_lpos was a wrapping data block. */ + wrapped = (DATA_WRAPS(data_ring, blk_lpos->begin) != DATA_WRAPS(data_ring, blk_lpos->next)); + + size = to_blk_size(size); + + next_lpos = get_next_lpos(data_ring, blk_lpos->begin, size); + + /* If the data block does not increase, there is nothing to do. */ + if (head_lpos - next_lpos < DATA_SIZE(data_ring)) { + blk = to_block(data_ring, blk_lpos->begin); + return &blk->data[0]; + } + + if (!data_push_tail(rb, data_ring, next_lpos - DATA_SIZE(data_ring))) + return NULL; + + /* The memory barrier involvement is the same as data_alloc:A. */ + if (!atomic_long_try_cmpxchg(&data_ring->head_lpos, &head_lpos, + next_lpos)) { /* LMM(data_realloc:A) */ + return NULL; + } + + blk = to_block(data_ring, blk_lpos->begin); + + if (DATA_WRAPS(data_ring, blk_lpos->begin) != DATA_WRAPS(data_ring, next_lpos)) { + struct prb_data_block *old_blk = blk; + + /* Wrapping data blocks store their data at the beginning. */ + blk = to_block(data_ring, 0); + + /* + * Store the ID on the wrapped block for consistency. + * The printk_ringbuffer does not actually use it. + */ + blk->id = id; + + if (!wrapped) { + /* + * Since the allocated space is now in the newly + * created wrapping data block, copy the content + * from the old data block. + */ + memcpy(&blk->data[0], &old_blk->data[0], + (blk_lpos->next - blk_lpos->begin) - sizeof(blk->id)); + } + } + + blk_lpos->next = next_lpos; + + return &blk->data[0]; +} + /* Return the number of bytes used by a data block. */ static unsigned int space_used(struct prb_data_ring *data_ring, struct prb_data_blk_lpos *blk_lpos) @@ -1104,6 +1251,206 @@ static const char *get_data(struct prb_data_ring *data_ring, return &db->data[0]; } +/* + * Attempt to transition the newest descriptor from committed back to reserved + * so that the record can be modified by a writer again. This is only possible + * if the descriptor is not yet finalized and the provided @caller_id matches. + */ +static struct prb_desc *desc_reopen_last(struct prb_desc_ring *desc_ring, + u32 caller_id, unsigned long *id_out) +{ + unsigned long prev_state_val; + enum desc_state d_state; + struct prb_desc desc; + struct prb_desc *d; + unsigned long id; + + id = atomic_long_read(&desc_ring->head_id); + + /* + * To reduce unnecessarily reopening, first check if the descriptor + * state and caller ID are correct. + */ + d_state = desc_read(desc_ring, id, &desc); + if (d_state != desc_committed || desc.info.caller_id != caller_id) + return NULL; + + d = to_desc(desc_ring, id); + + prev_state_val = DESC_SV(id, desc_committed); + + /* + * Guarantee the reserved state is stored before reading any + * record data. A full memory barrier is needed because @state_var + * modification is followed by reading. This pairs with _prb_commit:B. + * + * Memory barrier involvement: + * + * If desc_reopen_last:A reads from _prb_commit:B, then + * prb_reserve_in_last:A reads from _prb_commit:A. + * + * Relies on: + * + * WMB from _prb_commit:A to _prb_commit:B + * matching + * MB If desc_reopen_last:A to prb_reserve_in_last:A + */ + if (!atomic_long_try_cmpxchg(&d->state_var, &prev_state_val, + DESC_SV(id, desc_reserved))) { /* LMM(desc_reopen_last:A) */ + return NULL; + } + + *id_out = id; + return d; +} + +/** + * prb_reserve_in_last() - Re-reserve and extend the space in the ringbuffer + * used by the newest record. + * + * @e: The entry structure to setup. + * @rb: The ringbuffer to re-reserve and extend data in. + * @r: The record structure to allocate buffers for. + * @caller_id: The caller ID of the caller (reserving writer). + * + * This is the public function available to writers to re-reserve and extend + * data. + * + * The writer specifies the text size to extend (not the new total size) by + * setting the @text_buf_size field of @r. Extending dictionaries is not + * supported, so @dict_buf_size of @r should be set to 0. To ensure proper + * initialization of @r, prb_rec_init_wr() should be used. + * + * This function will fail if @caller_id does not match the caller ID of the + * newest record. In that case the caller must reserve new data using + * prb_reserve(). + * + * Context: Any context. Disables local interrupts on success. + * Return: true if text data could be extended, otherwise false. + * + * On success: + * + * - @r->text_buf points to the beginning of the entire text buffer. + * + * - @r->text_buf_size is set to the new total size of the buffer. + * + * - @r->dict_buf and @r->dict_buf_size are cleared because extending + * the dict buffer is not supported. + * + * - @r->info is not touched so that @r->info->text_len could be used + * to append the text. + * + * - prb_record_text_space() can be used on @e to query the new + * actually used space. + * + * Important: All @r->info fields will already be set with the current values + * for the record. I.e. @r->info->text_len will be less than + * @text_buf_size and @r->info->dict_len may be set, even though + * @dict_buf_size is 0. Writers can use @r->info->text_len to know + * where concatenation begins and writers should update + * @r->info->text_len after concatenating. + */ +bool prb_reserve_in_last(struct prb_reserved_entry *e, struct printk_ringbuffer *rb, + struct printk_record *r, u32 caller_id) +{ + unsigned int data_size; + struct prb_desc *d; + unsigned long id; + + local_irq_save(e->irqflags); + + /* Transition the newest descriptor back to the reserved state. */ + d = desc_reopen_last(&rb->desc_ring, caller_id, &id); + if (!d) { + local_irq_restore(e->irqflags); + goto fail_reopen; + } + + /* Now the writer has exclusive access: LMM(prb_reserve_in_last:A) */ + + /* + * Set the @e fields here so that prb_commit() can be used if + * anything fails from now on. + */ + e->rb = rb; + e->id = id; + + /* + * desc_reopen_last() checked the caller_id, but there was no + * exclusive access at that point. The descriptor may have + * changed since then. + */ + if (caller_id != d->info.caller_id) + goto fail; + + if (BLK_DATALESS(&d->text_blk_lpos)) { + if (WARN_ON_ONCE(d->info.text_len != 0)) { + pr_warn_once("wrong text_len value (%hu, expecting 0)\n", + d->info.text_len); + d->info.text_len = 0; + } + + if (!data_check_size(&rb->text_data_ring, r->text_buf_size)) + goto fail; + + r->text_buf = data_alloc(rb, &rb->text_data_ring, r->text_buf_size, + &d->text_blk_lpos, id); + } else { + if (!get_data(&rb->text_data_ring, &d->text_blk_lpos, &data_size)) + goto fail; + + /* + * Increase the buffer size to include the original size. If + * the meta data (@text_len) is not sane, use the full data + * block size. + */ + if (WARN_ON_ONCE(d->info.text_len > data_size)) { + pr_warn_once("wrong text_len value (%hu, expecting <=%u)\n", + d->info.text_len, data_size); + d->info.text_len = data_size; + } + r->text_buf_size += d->info.text_len; + + if (!data_check_size(&rb->text_data_ring, r->text_buf_size)) + goto fail; + + r->text_buf = data_realloc(rb, &rb->text_data_ring, r->text_buf_size, + &d->text_blk_lpos, id); + } + if (r->text_buf_size && !r->text_buf) + goto fail; + + /* Although dictionary data may be in use, it cannot be extended. */ + r->dict_buf = NULL; + r->dict_buf_size = 0; + + r->info = &d->info; + + e->text_space = space_used(&rb->text_data_ring, &d->text_blk_lpos); + + return true; +fail: + prb_commit(e); + /* prb_commit() re-enabled interrupts. */ +fail_reopen: + /* Make it clear to the caller that the re-reserve failed. */ + memset(r, 0, sizeof(*r)); + return false; +} + +/* + * 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) +{ + 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) */ +} + /** * prb_reserve() - Reserve space in the ringbuffer. * @@ -1197,6 +1544,15 @@ bool prb_reserve(struct prb_reserved_entry *e, struct printk_ringbuffer *rb, else d->info.seq = seq + DESCS_COUNT(desc_ring); + /* + * New data is about to be reserved. Once that happens, previous + * descriptors are no longer able to be extended. Finalize the + * previous descriptor now so that it can be made available to + * readers. (For seq==0 there is no previous descriptor.) + */ + if (d->info.seq > 0) + desc_make_final(desc_ring, DESC_ID(id - 1)); + r->text_buf = data_alloc(rb, &rb->text_data_ring, r->text_buf_size, &d->text_blk_lpos, id); /* If text data allocation fails, a data-less record is committed. */ @@ -1227,33 +1583,40 @@ fail: return false; } -/** - * prb_commit() - Commit (previously reserved) data to the ringbuffer. - * - * @e: The entry containing the reserved data information. - * - * This is the public function available to writers to commit data. - * - * Context: Any context. Enables local interrupts. - */ -void prb_commit(struct prb_reserved_entry *e) +/* Commit the data (possibly finalizing it) and restore interrupts. */ +static void _prb_commit(struct prb_reserved_entry *e, unsigned long state_val) { struct prb_desc_ring *desc_ring = &e->rb->desc_ring; struct prb_desc *d = to_desc(desc_ring, e->id); unsigned long prev_state_val = DESC_SV(e->id, desc_reserved); - /* Now the writer has finished all writing: LMM(prb_commit:A) */ + /* Now the writer has finished all writing: LMM(_prb_commit:A) */ /* * Set the descriptor as committed. See "ABA Issues" about why * cmpxchg() instead of set() is used. * - * Guarantee all record data is stored before the descriptor state - * is stored as committed. A write memory barrier is sufficient for - * this. This pairs with desc_read:B. + * 1 Guarantee all record data is stored before the descriptor state + * is stored as committed. A write memory barrier is sufficient + * for this. This pairs with desc_read:B and desc_reopen_last:A. + * + * 2. Guarantee the descriptor state is stored as committed before + * re-checking the head ID in order to possibly finalize this + * descriptor. This pairs with desc_reserve:D. + * + * Memory barrier involvement: + * + * If prb_commit:A reads from desc_reserve:D, then + * desc_make_final:A reads from _prb_commit:B. + * + * Relies on: + * + * MB _prb_commit:B to prb_commit:A + * matching + * MB desc_reserve:D to desc_make_final:A */ if (!atomic_long_try_cmpxchg(&d->state_var, &prev_state_val, - DESC_SV(e->id, desc_committed))) { /* LMM(prb_commit:B) */ + DESC_SV(e->id, state_val))) { /* LMM(_prb_commit:B) */ WARN_ON_ONCE(1); } @@ -1261,6 +1624,59 @@ void prb_commit(struct prb_reserved_entry *e) local_irq_restore(e->irqflags); } +/** + * prb_commit() - Commit (previously reserved) data to the ringbuffer. + * + * @e: The entry containing the reserved data information. + * + * This is the public function available to writers to commit data. + * + * Note that the data is not yet available to readers until it is finalized. + * Finalizing happens automatically when space for the next record is + * reserved. + * + * See prb_final_commit() for a version of this function that finalizes + * immediately. + * + * Context: Any context. Enables local interrupts. + */ +void prb_commit(struct prb_reserved_entry *e) +{ + struct prb_desc_ring *desc_ring = &e->rb->desc_ring; + unsigned long head_id; + + _prb_commit(e, desc_committed); + + /* + * If this descriptor is no longer the head (i.e. a new record has + * been allocated), extending the data for this record is no longer + * allowed and therefore it must be finalized. + */ + 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); +} + +/** + * prb_final_commit() - Commit and finalize (previously reserved) data to + * the ringbuffer. + * + * @e: The entry containing the reserved data information. + * + * This is the public function available to writers to commit+finalize data. + * + * By finalizing, the data is made immediately available to readers. + * + * This function should only be used if there are no intentions of extending + * this data using prb_reserve_in_last(). + * + * Context: Any context. Enables local interrupts. + */ +void prb_final_commit(struct prb_reserved_entry *e) +{ + _prb_commit(e, desc_finalized); +} + /* * Count the number of lines in provided text. All text has at least 1 line * (even if @text_size is 0). Each '\n' processed is counted as an additional @@ -1312,7 +1728,7 @@ static bool copy_data(struct prb_data_ring *data_ring, * because of the trailing alignment padding. */ if (WARN_ON_ONCE(data_size < (unsigned int)len)) { - pr_warn_once("wrong data size (%u, expecting %hu) for data: %.*s\n", + pr_warn_once("wrong data size (%u, expecting >=%hu) for data: %.*s\n", data_size, len, data_size, data); return false; } @@ -1333,16 +1749,16 @@ static bool copy_data(struct prb_data_ring *data_ring, /* * This is an extended version of desc_read(). It gets a copy of a specified - * descriptor. However, it also verifies that the record is committed and has + * descriptor. However, it also verifies that the record is finalized and has * the sequence number @seq. On success, 0 is returned. * * Error return values: - * -EINVAL: A committed record with sequence number @seq does not exist. - * -ENOENT: A committed record with sequence number @seq exists, but its data + * -EINVAL: A finalized record with sequence number @seq does not exist. + * -ENOENT: A finalized record with sequence number @seq exists, but its data * is not available. This is a valid record, so readers should * continue with the next record. */ -static int desc_read_committed_seq(struct prb_desc_ring *desc_ring, +static int desc_read_finalized_seq(struct prb_desc_ring *desc_ring, unsigned long id, u64 seq, struct prb_desc *desc_out) { @@ -1353,11 +1769,12 @@ static int desc_read_committed_seq(struct prb_desc_ring *desc_ring, /* * An unexpected @id (desc_miss) or @seq mismatch means the record - * does not exist. A descriptor in the reserved state means the - * record does not yet exist for the reader. + * does not exist. A descriptor in the reserved or committed state + * means the record does not yet exist for the reader. */ if (d_state == desc_miss || d_state == desc_reserved || + d_state == desc_committed || desc_out->info.seq != seq) { return -EINVAL; } @@ -1379,7 +1796,7 @@ static int desc_read_committed_seq(struct prb_desc_ring *desc_ring, * Copy the ringbuffer data from the record with @seq to the provided * @r buffer. On success, 0 is returned. * - * See desc_read_committed_seq() for error return values. + * See desc_read_finalized_seq() for error return values. */ static int prb_read(struct printk_ringbuffer *rb, u64 seq, struct printk_record *r, unsigned int *line_count) @@ -1395,7 +1812,7 @@ static int prb_read(struct printk_ringbuffer *rb, u64 seq, id = DESC_ID(atomic_long_read(state_var)); /* Get a local copy of the correct descriptor (if available). */ - err = desc_read_committed_seq(desc_ring, id, seq, &desc); + err = desc_read_finalized_seq(desc_ring, id, seq, &desc); /* * If @r is NULL, the caller is only interested in the availability @@ -1425,8 +1842,8 @@ static int prb_read(struct printk_ringbuffer *rb, u64 seq, r->info->dict_len = 0; } - /* Ensure the record is still committed and has the same @seq. */ - return desc_read_committed_seq(desc_ring, id, seq, &desc); + /* Ensure the record is still finalized and has the same @seq. */ + return desc_read_finalized_seq(desc_ring, id, seq, &desc); } /* Get the sequence number of the tail descriptor. */ @@ -1444,9 +1861,9 @@ static u64 prb_first_seq(struct printk_ringbuffer *rb) /* * This loop will not be infinite because the tail is - * _always_ in the committed or reusable state. + * _always_ in the finalized or reusable state. */ - if (d_state == desc_committed || d_state == desc_reusable) + if (d_state == desc_finalized || d_state == desc_reusable) break; /* @@ -1473,8 +1890,8 @@ static u64 prb_first_seq(struct printk_ringbuffer *rb) } /* - * Non-blocking read of a record. Updates @seq to the last committed record - * (which may have no data). + * Non-blocking read of a record. Updates @seq to the last finalized record + * (which may have no data available). * * See the description of prb_read_valid() and prb_read_valid_info() * for details. @@ -1500,7 +1917,7 @@ static bool _prb_read_valid(struct printk_ringbuffer *rb, u64 *seq, (*seq)++; } else { - /* Non-existent/non-committed record. Must stop. */ + /* Non-existent/non-finalized record. Must stop. */ return false; } } diff --git a/kernel/printk/printk_ringbuffer.h b/kernel/printk/printk_ringbuffer.h index a9d85a6727b1..853ea62dc5f2 100644 --- a/kernel/printk/printk_ringbuffer.h +++ b/kernel/printk/printk_ringbuffer.h @@ -116,7 +116,8 @@ struct prb_reserved_entry { enum desc_state { desc_miss = -1, /* ID mismatch (pseudo state) */ desc_reserved = 0x0, /* reserved, in use by writer */ - desc_committed = 0x1, /* committed by writer */ + desc_committed = 0x1, /* committed by writer, could get reopened */ + desc_finalized = 0x2, /* committed, no further modification allowed */ desc_reusable = 0x3, /* free, not yet used by any writer */ }; @@ -327,7 +328,10 @@ static inline void prb_rec_init_wr(struct printk_record *r, bool prb_reserve(struct prb_reserved_entry *e, struct printk_ringbuffer *rb, struct printk_record *r); +bool prb_reserve_in_last(struct prb_reserved_entry *e, struct printk_ringbuffer *rb, + struct printk_record *r, u32 caller_id); void prb_commit(struct prb_reserved_entry *e); +void prb_final_commit(struct prb_reserved_entry *e); void prb_init(struct printk_ringbuffer *rb, char *text_buf, unsigned int text_buf_size, |