diff options
author | Linus Torvalds | 2020-10-13 15:58:10 -0700 |
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committer | Linus Torvalds | 2020-10-13 15:58:10 -0700 |
commit | d594d8f411d47bf7b583ec3474b11fec348c88bb (patch) | |
tree | 0f0df70d11f31b006684b48e5b973f9ae3a7b679 /Documentation/admin-guide/kdump | |
parent | 029f56db6ac248769f2c260bfaf3c3c0e23e904c (diff) | |
parent | 70333f4ff9c16dd82a2667080c3ae48fe30a3cb4 (diff) |
Merge tag 'printk-for-5.10' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux
Pull printk updates from Petr Mladek:
"The big new thing is the fully lockless ringbuffer implementation,
including the support for continuous lines. It will allow to store and
read messages in any situation wihtout the risk of deadlocks and
without the need of temporary per-CPU buffers.
The access is still serialized by logbuf_lock. It synchronizes few
more operations, for example, temporary buffer for formatting the
message, syslog and kmsg_dump operations. The lock removal is being
discussed and should be ready for the next release.
The continuous lines are handled exactly the same way as before to
avoid regressions in user space. It means that they are appended to
the last message when the caller is the same. Only the last message
can be extended.
The data ring includes plain text of the messages. Except for an
integer at the beginning of each message that points back to the
descriptor ring with other metadata.
The dictionary has to stay. journalctl uses it to filter the log. It
allows to show messages related to a given device. The dictionary
values are stored in the descriptor ring with the other metadata.
This is the first part of the printk rework as discussed at Plumbers
2019, see https://lore.kernel.org/r/87k1acz5rx.fsf@linutronix.de. The
next big step will be handling consoles by kthreads during the normal
system operation. It will require special handling of situations when
the kthreads could not get scheduled, for example, early boot,
suspend, panic.
Other changes:
- Add John Ogness as a reviewer for printk subsystem. He is author of
the rework and is familiar with the code and history.
- Fix locking in serial8250_do_startup() to prevent lockdep report.
- Few code cleanups"
* tag 'printk-for-5.10' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux: (27 commits)
printk: Use fallthrough pseudo-keyword
printk: reduce setup_text_buf size to LOG_LINE_MAX
printk: avoid and/or handle record truncation
printk: remove dict ring
printk: move dictionary keys to dev_printk_info
printk: move printk_info into separate array
printk: reimplement log_cont using record extension
printk: ringbuffer: add finalization/extension support
printk: ringbuffer: change representation of states
printk: ringbuffer: clear initial reserved fields
printk: ringbuffer: add BLK_DATALESS() macro
printk: ringbuffer: relocate get_data()
printk: ringbuffer: avoid memcpy() on state_var
printk: ringbuffer: fix setting state in desc_read()
kernel.h: Move oops_in_progress to printk.h
scripts/gdb: update for lockless printk ringbuffer
scripts/gdb: add utils.read_ulong()
docs: vmcoreinfo: add lockless printk ringbuffer vmcoreinfo
printk: reduce LOG_BUF_SHIFT range for H8300
printk: ringbuffer: support dataless records
...
Diffstat (limited to 'Documentation/admin-guide/kdump')
-rw-r--r-- | Documentation/admin-guide/kdump/gdbmacros.txt | 159 | ||||
-rw-r--r-- | Documentation/admin-guide/kdump/vmcoreinfo.rst | 131 |
2 files changed, 211 insertions, 79 deletions
diff --git a/Documentation/admin-guide/kdump/gdbmacros.txt b/Documentation/admin-guide/kdump/gdbmacros.txt index 220d0a80ca2c..82aecdcae8a6 100644 --- a/Documentation/admin-guide/kdump/gdbmacros.txt +++ b/Documentation/admin-guide/kdump/gdbmacros.txt @@ -170,57 +170,103 @@ document trapinfo address the kernel panicked. end -define dump_log_idx - set $idx = $arg0 - if ($argc > 1) - set $prev_flags = $arg1 +define dump_record + set var $desc = $arg0 + set var $info = $arg1 + if ($argc > 2) + set var $prev_flags = $arg2 else - set $prev_flags = 0 + set var $prev_flags = 0 end - set $msg = ((struct printk_log *) (log_buf + $idx)) - set $prefix = 1 - set $newline = 1 - set $log = log_buf + $idx + sizeof(*$msg) - - # prev & LOG_CONT && !(msg->flags & LOG_PREIX) - if (($prev_flags & 8) && !($msg->flags & 4)) - set $prefix = 0 + + set var $prefix = 1 + set var $newline = 1 + + set var $begin = $desc->text_blk_lpos.begin % (1U << prb->text_data_ring.size_bits) + set var $next = $desc->text_blk_lpos.next % (1U << prb->text_data_ring.size_bits) + + # handle data-less record + if ($begin & 1) + set var $text_len = 0 + set var $log = "" + else + # handle wrapping data block + if ($begin > $next) + set var $begin = 0 + end + + # skip over descriptor id + set var $begin = $begin + sizeof(long) + + # handle truncated message + if ($next - $begin < $info->text_len) + set var $text_len = $next - $begin + else + set var $text_len = $info->text_len + end + + set var $log = &prb->text_data_ring.data[$begin] + end + + # prev & LOG_CONT && !(info->flags & LOG_PREIX) + if (($prev_flags & 8) && !($info->flags & 4)) + set var $prefix = 0 end - # msg->flags & LOG_CONT - if ($msg->flags & 8) + # info->flags & LOG_CONT + if ($info->flags & 8) # (prev & LOG_CONT && !(prev & LOG_NEWLINE)) if (($prev_flags & 8) && !($prev_flags & 2)) - set $prefix = 0 + set var $prefix = 0 end - # (!(msg->flags & LOG_NEWLINE)) - if (!($msg->flags & 2)) - set $newline = 0 + # (!(info->flags & LOG_NEWLINE)) + if (!($info->flags & 2)) + set var $newline = 0 end end if ($prefix) - printf "[%5lu.%06lu] ", $msg->ts_nsec / 1000000000, $msg->ts_nsec % 1000000000 + printf "[%5lu.%06lu] ", $info->ts_nsec / 1000000000, $info->ts_nsec % 1000000000 end - if ($msg->text_len != 0) - eval "printf \"%%%d.%ds\", $log", $msg->text_len, $msg->text_len + if ($text_len) + eval "printf \"%%%d.%ds\", $log", $text_len, $text_len end if ($newline) printf "\n" end - if ($msg->dict_len > 0) - set $dict = $log + $msg->text_len - set $idx = 0 - set $line = 1 - while ($idx < $msg->dict_len) - if ($line) - printf " " - set $line = 0 + + # handle dictionary data + + set var $dict = &$info->dev_info.subsystem[0] + set var $dict_len = sizeof($info->dev_info.subsystem) + if ($dict[0] != '\0') + printf " SUBSYSTEM=" + set var $idx = 0 + while ($idx < $dict_len) + set var $c = $dict[$idx] + if ($c == '\0') + loop_break + else + if ($c < ' ' || $c >= 127 || $c == '\\') + printf "\\x%02x", $c + else + printf "%c", $c + end end - set $c = $dict[$idx] + set var $idx = $idx + 1 + end + printf "\n" + end + + set var $dict = &$info->dev_info.device[0] + set var $dict_len = sizeof($info->dev_info.device) + if ($dict[0] != '\0') + printf " DEVICE=" + set var $idx = 0 + while ($idx < $dict_len) + set var $c = $dict[$idx] if ($c == '\0') - printf "\n" - set $line = 1 + loop_break else if ($c < ' ' || $c >= 127 || $c == '\\') printf "\\x%02x", $c @@ -228,33 +274,46 @@ define dump_log_idx printf "%c", $c end end - set $idx = $idx + 1 + set var $idx = $idx + 1 end printf "\n" end end -document dump_log_idx - Dump a single log given its index in the log buffer. The first - parameter is the index into log_buf, the second is optional and - specified the previous log buffer's flags, used for properly - formatting continued lines. +document dump_record + Dump a single record. The first parameter is the descriptor, + the second parameter is the info, the third parameter is + optional and specifies the previous record's flags, used for + properly formatting continued lines. end define dmesg - set $i = log_first_idx - set $end_idx = log_first_idx - set $prev_flags = 0 + # definitions from kernel/printk/printk_ringbuffer.h + set var $desc_committed = 1 + set var $desc_finalized = 2 + set var $desc_sv_bits = sizeof(long) * 8 + set var $desc_flags_shift = $desc_sv_bits - 2 + set var $desc_flags_mask = 3 << $desc_flags_shift + set var $id_mask = ~$desc_flags_mask + + set var $desc_count = 1U << prb->desc_ring.count_bits + set var $prev_flags = 0 + + set var $id = prb->desc_ring.tail_id.counter + set var $end_id = prb->desc_ring.head_id.counter while (1) - set $msg = ((struct printk_log *) (log_buf + $i)) - if ($msg->len == 0) - set $i = 0 - else - dump_log_idx $i $prev_flags - set $i = $i + $msg->len - set $prev_flags = $msg->flags + set var $desc = &prb->desc_ring.descs[$id % $desc_count] + set var $info = &prb->desc_ring.infos[$id % $desc_count] + + # skip non-committed record + set var $state = 3 & ($desc->state_var.counter >> $desc_flags_shift) + if ($state == $desc_committed || $state == $desc_finalized) + dump_record $desc $info $prev_flags + set var $prev_flags = $info->flags end - if ($i == $end_idx) + + set var $id = ($id + 1) & $id_mask + if ($id == $end_id) loop_break end end diff --git a/Documentation/admin-guide/kdump/vmcoreinfo.rst b/Documentation/admin-guide/kdump/vmcoreinfo.rst index 2baad0bfb09d..e44a6c01f336 100644 --- a/Documentation/admin-guide/kdump/vmcoreinfo.rst +++ b/Documentation/admin-guide/kdump/vmcoreinfo.rst @@ -189,50 +189,123 @@ from this. Free areas descriptor. User-space tools use this value to iterate the free_area ranges. MAX_ORDER is used by the zone buddy allocator. -log_first_idx +prb +--- + +A pointer to the printk ringbuffer (struct printk_ringbuffer). This +may be pointing to the static boot ringbuffer or the dynamically +allocated ringbuffer, depending on when the the core dump occurred. +Used by user-space tools to read the active kernel log buffer. + +printk_rb_static +---------------- + +A pointer to the static boot printk ringbuffer. If @prb has a +different value, this is useful for viewing the initial boot messages, +which may have been overwritten in the dynamically allocated +ringbuffer. + +clear_seq +--------- + +The sequence number of the printk() record after the last clear +command. It indicates the first record after the last +SYSLOG_ACTION_CLEAR, like issued by 'dmesg -c'. Used by user-space +tools to dump a subset of the dmesg log. + +printk_ringbuffer +----------------- + +The size of a printk_ringbuffer structure. This structure contains all +information required for accessing the various components of the +kernel log buffer. + +(printk_ringbuffer, desc_ring|text_data_ring|dict_data_ring|fail) +----------------------------------------------------------------- + +Offsets for the various components of the printk ringbuffer. Used by +user-space tools to view the kernel log buffer without requiring the +declaration of the structure. + +prb_desc_ring ------------- -Index of the first record stored in the buffer log_buf. Used by -user-space tools to read the strings in the log_buf. +The size of the prb_desc_ring structure. This structure contains +information about the set of record descriptors. -log_buf -------- +(prb_desc_ring, count_bits|descs|head_id|tail_id) +------------------------------------------------- + +Offsets for the fields describing the set of record descriptors. Used +by user-space tools to be able to traverse the descriptors without +requiring the declaration of the structure. + +prb_desc +-------- + +The size of the prb_desc structure. This structure contains +information about a single record descriptor. + +(prb_desc, info|state_var|text_blk_lpos|dict_blk_lpos) +------------------------------------------------------ + +Offsets for the fields describing a record descriptors. Used by +user-space tools to be able to read descriptors without requiring +the declaration of the structure. + +prb_data_blk_lpos +----------------- + +The size of the prb_data_blk_lpos structure. This structure contains +information about where the text or dictionary data (data block) is +located within the respective data ring. + +(prb_data_blk_lpos, begin|next) +------------------------------- -Console output is written to the ring buffer log_buf at index -log_first_idx. Used to get the kernel log. +Offsets for the fields describing the location of a data block. Used +by user-space tools to be able to locate data blocks without +requiring the declaration of the structure. -log_buf_len +printk_info ----------- -log_buf's length. +The size of the printk_info structure. This structure contains all +the meta-data for a record. -clear_idx ---------- +(printk_info, seq|ts_nsec|text_len|dict_len|caller_id) +------------------------------------------------------ -The index that the next printk() record to read after the last clear -command. It indicates the first record after the last SYSLOG_ACTION -_CLEAR, like issued by 'dmesg -c'. Used by user-space tools to dump -the dmesg log. +Offsets for the fields providing the meta-data for a record. Used by +user-space tools to be able to read the information without requiring +the declaration of the structure. -log_next_idx ------------- +prb_data_ring +------------- -The index of the next record to store in the buffer log_buf. Used to -compute the index of the current buffer position. +The size of the prb_data_ring structure. This structure contains +information about a set of data blocks. -printk_log ----------- +(prb_data_ring, size_bits|data|head_lpos|tail_lpos) +--------------------------------------------------- -The size of a structure printk_log. Used to compute the size of -messages, and extract dmesg log. It encapsulates header information for -log_buf, such as timestamp, syslog level, etc. +Offsets for the fields describing a set of data blocks. Used by +user-space tools to be able to access the data blocks without +requiring the declaration of the structure. -(printk_log, ts_nsec|len|text_len|dict_len) -------------------------------------------- +atomic_long_t +------------- + +The size of the atomic_long_t structure. Used by user-space tools to +be able to copy the full structure, regardless of its +architecture-specific implementation. + +(atomic_long_t, counter) +------------------------ -It represents field offsets in struct printk_log. User space tools -parse it and check whether the values of printk_log's members have been -changed. +Offset for the long value of an atomic_long_t variable. Used by +user-space tools to access the long value without requiring the +architecture-specific declaration. (free_area.free_list, MIGRATE_TYPES) ------------------------------------ |