summaryrefslogtreecommitdiff
path: root/Documentation/admin-guide
diff options
context:
space:
mode:
authorGuilherme G. Piccoli <gpiccoli@igalia.com>2022-03-23 16:07:09 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2022-03-23 19:00:35 -0700
commitf953f140f318a641c443b0b8c618155ed90a7a10 (patch)
tree817becbe26174902383e80312a20425155d194c2 /Documentation/admin-guide
parent8d470a45d1a65e6a308aeee5da7f5b37d3303c04 (diff)
panic: move panic_print before kmsg dumpers
The panic_print setting allows users to collect more information in a panic event, like memory stats, tasks, CPUs backtraces, etc. This is an interesting debug mechanism, but currently the print event happens *after* kmsg_dump(), meaning that pstore, for example, cannot collect a dmesg with the panic_print extra information. This patch changes that in 2 steps: (a) The panic_print setting allows to replay the existing kernel log buffer to the console (bit 5), besides the extra information dump. This functionality makes sense only at the end of the panic() function. So, we hereby allow to distinguish the two situations by a new boolean parameter in the function panic_print_sys_info(). (b) With the above change, we can safely call panic_print_sys_info() before kmsg_dump(), allowing to dump the extra information when using pstore or other kmsg dumpers. The additional messages from panic_print could overwrite the oldest messages when the buffer is full. The only reasonable solution is to use a large enough log buffer, hence we added an advice into the kernel parameters documentation about that. Link: https://lkml.kernel.org/r/20220214141308.841525-1-gpiccoli@igalia.com Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com> Acked-by: Baoquan He <bhe@redhat.com> Reviewed-by: Petr Mladek <pmladek@suse.com> Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org> Cc: Feng Tang <feng.tang@intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/admin-guide')
-rw-r--r--Documentation/admin-guide/kernel-parameters.txt4
1 files changed, 4 insertions, 0 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 6287f6be4a98..a18e30a95931 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3727,6 +3727,10 @@
bit 4: print ftrace buffer
bit 5: print all printk messages in buffer
bit 6: print all CPUs backtrace (if available in the arch)
+ *Be aware* that this option may print a _lot_ of lines,
+ so there are risks of losing older messages in the log.
+ Use this option carefully, maybe worth to setup a
+ bigger log buffer with "log_buf_len" along with this.
panic_on_taint= Bitmask for conditionally calling panic() in add_taint()
Format: <hex>[,nousertaint]