diff options
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 8 | ||||
| -rw-r--r-- | kernel/printk/internal.h | 1 | ||||
| -rw-r--r-- | kernel/printk/printk.c | 20 | ||||
| -rw-r--r-- | kernel/printk/printk_ringbuffer.c | 13 |
4 files changed, 36 insertions, 6 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 05f5935eeac8..961bc82f0599 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -5013,6 +5013,14 @@ Format: <bool> default: 0 (auto_verbose is enabled) + printk.debug_non_panic_cpus= + Allows storing messages from non-panic CPUs into + the printk log buffer during panic(). They are + flushed to consoles by the panic-CPU on + a best-effort basis. + Format: <bool> (1/Y/y=enable, 0/N/n=disable) + Default: disabled + printk.devkmsg={on,off,ratelimit} Control writing to /dev/kmsg. on - unlimited logging to /dev/kmsg from userspace diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h index a91bdf802967..48a24e7b309d 100644 --- a/kernel/printk/internal.h +++ b/kernel/printk/internal.h @@ -64,6 +64,7 @@ struct dev_printk_info; extern struct printk_ringbuffer *prb; extern bool printk_kthreads_running; +extern bool debug_non_panic_cpus; __printf(4, 0) int vprintk_store(int facility, int level, diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 2590498d8353..74b4734a87b9 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -2375,6 +2375,22 @@ void printk_legacy_allow_panic_sync(void) } } +bool __read_mostly debug_non_panic_cpus; + +#ifdef CONFIG_PRINTK_CALLER +static int __init debug_non_panic_cpus_setup(char *str) +{ + debug_non_panic_cpus = true; + pr_info("allow messages from non-panic CPUs in panic()\n"); + + return 0; +} +early_param("debug_non_panic_cpus", debug_non_panic_cpus_setup); +module_param(debug_non_panic_cpus, bool, 0644); +MODULE_PARM_DESC(debug_non_panic_cpus, + "allow messages from non-panic CPUs in panic()"); +#endif + asmlinkage int vprintk_emit(int facility, int level, const struct dev_printk_info *dev_info, const char *fmt, va_list args) @@ -2391,7 +2407,9 @@ asmlinkage int vprintk_emit(int facility, int level, * non-panic CPUs are generating any messages, they will be * silently dropped. */ - if (other_cpu_in_panic() && !panic_triggering_all_cpu_backtrace) + if (other_cpu_in_panic() && + !debug_non_panic_cpus && + !panic_triggering_all_cpu_backtrace) return 0; printk_get_console_flush_type(&ft); 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; + } } } |