diff options
| author | Donghyeok Choe <d7271.choe@samsung.com> | 2025-03-18 11:23:20 +0900 |
|---|---|---|
| committer | Petr Mladek <pmladek@suse.com> | 2025-03-20 15:48:36 +0100 |
| commit | c1aa3daa517292303d98ff61f0440c354669f948 (patch) | |
| tree | 01fc3b28e2e1ac7a68c3f5ead9229252ceaba96d /kernel/printk/printk_ringbuffer.c | |
| parent | 2f1f7787b6b8648f3ceefc59192489052644c6c7 (diff) | |
printk/panic: Add option to allow non-panic CPUs to write to the ring buffer.
Commit 779dbc2e78d7 ("printk: Avoid non-panic CPUs writing to ringbuffer")
aimed to isolate panic-related messages. However, when panic() itself
malfunctions, messages from non-panic CPUs become crucial for debugging.
While commit bcc954c6caba ("printk/panic: Allow cpu backtraces to
be written into ringbuffer during panic") enables non-panic CPU
backtraces, it may not provide sufficient diagnostic information.
Introduce the "debug_non_panic_cpus" command-line option, enabling
non-panic CPU messages to be stored in the ring buffer during a panic.
This also prevents discarding non-finalized messages from non-panic CPUs
during console flushing, providing a more comprehensive view of system
state during critical failures.
Link: https://lore.kernel.org/all/Z8cLEkqLL2IOyNIj@pathway/
Signed-off-by: Donghyeok Choe <d7271.choe@samsung.com>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20250318022320.2428155-1-d7271.choe@samsung.com
[pmladek@suse.com: Added documentation, added module_parameter, removed printk_ prefix.]
Tested-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Diffstat (limited to 'kernel/printk/printk_ringbuffer.c')
| -rw-r--r-- | kernel/printk/printk_ringbuffer.c | 13 |
1 files changed, 8 insertions, 5 deletions
diff --git a/kernel/printk/printk_ringbuffer.c b/kernel/printk/printk_ringbuffer.c index 88e8f3a61922..d9fb053cff67 100644 --- a/kernel/printk/printk_ringbuffer.c +++ b/kernel/printk/printk_ringbuffer.c @@ -2133,9 +2133,9 @@ static bool _prb_read_valid(struct printk_ringbuffer *rb, u64 *seq, * 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. + * non-existent/non-finalized record unless non-panic + * CPUs are still running and their debugging is + * explicitly enabled. * * Note that new messages printed on panic CPU are * finalized when we are here. The only exception @@ -2143,10 +2143,13 @@ static bool _prb_read_valid(struct printk_ringbuffer *rb, u64 *seq, * 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))) + if (this_cpu_in_panic() && + (!debug_non_panic_cpus || legacy_allow_panic_sync) && + ((*seq + 1) < prb_next_reserve_seq(rb))) { (*seq)++; - else + } else { return false; + } } } |