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Diffstat (limited to '')
| -rw-r--r-- | debian/patches-rt/0094-printk-ringbuffer-Skip-non-finalized-records-in-pani.patch | 68 |
1 files changed, 68 insertions, 0 deletions
diff --git a/debian/patches-rt/0094-printk-ringbuffer-Skip-non-finalized-records-in-pani.patch b/debian/patches-rt/0094-printk-ringbuffer-Skip-non-finalized-records-in-pani.patch new file mode 100644 index 000000000..56c675cea --- /dev/null +++ b/debian/patches-rt/0094-printk-ringbuffer-Skip-non-finalized-records-in-pani.patch @@ -0,0 +1,68 @@ +From: John Ogness <john.ogness@linutronix.de> +Date: Fri, 13 Oct 2023 10:23:11 +0000 +Subject: [PATCH 094/134] printk: ringbuffer: Skip non-finalized records in + panic +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.6/older/patches-6.6.7-rt18.tar.xz + +Normally a reader will stop once reaching a non-finalized +record. However, when a panic happens, writers from other CPUs +(or an interrupted context on the panic CPU) may have been +writing a record and were unable to finalize it. The panic CPU +will reserve/commit/finalize its panic records, but these will +be located after the non-finalized records. This results in +panic() not flushing the panic messages. + +Extend _prb_read_valid() to skip over non-finalized records if +on the panic CPU. + +Fixes: 896fbe20b4e2 ("printk: use the lockless ringbuffer") +Signed-off-by: John Ogness <john.ogness@linutronix.de> +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +--- + kernel/printk/printk_ringbuffer.c | 28 ++++++++++++++++++++++++++-- + 1 file changed, 26 insertions(+), 2 deletions(-) + +--- a/kernel/printk/printk_ringbuffer.c ++++ b/kernel/printk/printk_ringbuffer.c +@@ -2107,6 +2107,10 @@ u64 prb_next_reserve_seq(struct printk_r + * + * On failure @seq is updated to a record that is not yet available to the + * reader, but it will be the next record available to the reader. ++ * ++ * Note: When the current CPU is in panic, this function will skip over any ++ * non-existent/non-finalized records in order to allow the panic CPU ++ * to print any and all records that have been finalized. + */ + static bool _prb_read_valid(struct printk_ringbuffer *rb, u64 *seq, + struct printk_record *r, unsigned int *line_count) +@@ -2129,8 +2133,28 @@ static bool _prb_read_valid(struct print + (*seq)++; + + } else { +- /* Non-existent/non-finalized record. Must stop. */ +- return false; ++ /* ++ * Non-existent/non-finalized record. Must stop. ++ * ++ * For panic situations it cannot be expected that ++ * non-finalized records will become finalized. But ++ * 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. ++ * ++ * Note that new messages printed on panic CPU are ++ * finalized when we are here. The only exception ++ * might be the last message without trailing newline. ++ * 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))) ++ (*seq)++; ++ else ++ return false; + } + } + |