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-rw-r--r--debian/patches-rt/0103-printk-change-console_seq-to-atomic64_t.patch132
1 files changed, 132 insertions, 0 deletions
diff --git a/debian/patches-rt/0103-printk-change-console_seq-to-atomic64_t.patch b/debian/patches-rt/0103-printk-change-console_seq-to-atomic64_t.patch
new file mode 100644
index 000000000..6647ecd6c
--- /dev/null
+++ b/debian/patches-rt/0103-printk-change-console_seq-to-atomic64_t.patch
@@ -0,0 +1,132 @@
+From ebdec06c58c4330925d5603649542827bf7bff25 Mon Sep 17 00:00:00 2001
+From: John Ogness <john.ogness@linutronix.de>
+Date: Mon, 30 Nov 2020 01:42:05 +0106
+Subject: [PATCH 103/323] printk: change @console_seq to atomic64_t
+Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.204-rt100.tar.xz
+
+In preparation for atomic printing, change @console_seq to atomic
+so that it can be accessed without requiring @console_sem.
+
+Signed-off-by: John Ogness <john.ogness@linutronix.de>
+Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
+---
+ kernel/printk/printk.c | 34 +++++++++++++++++++---------------
+ 1 file changed, 19 insertions(+), 15 deletions(-)
+
+diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
+index 0ae184675e86..2bc9904fd8ab 100644
+--- a/kernel/printk/printk.c
++++ b/kernel/printk/printk.c
+@@ -368,12 +368,13 @@ static u64 syslog_seq;
+ static size_t syslog_partial;
+ static bool syslog_time;
+
+-/* All 3 protected by @console_sem. */
+-/* the next printk record to write to the console */
+-static u64 console_seq;
++/* Both protected by @console_sem. */
+ static u64 exclusive_console_stop_seq;
+ static unsigned long console_dropped;
+
++/* the next printk record to write to the console */
++static atomic64_t console_seq = ATOMIC64_INIT(0);
++
+ struct latched_seq {
+ seqcount_latch_t latch;
+ u64 val[2];
+@@ -2273,7 +2274,7 @@ EXPORT_SYMBOL(printk);
+ #define prb_first_valid_seq(rb) 0
+
+ static u64 syslog_seq;
+-static u64 console_seq;
++static atomic64_t console_seq = ATOMIC64_INIT(0);
+ static u64 exclusive_console_stop_seq;
+ static unsigned long console_dropped;
+
+@@ -2588,6 +2589,7 @@ void console_unlock(void)
+ bool do_cond_resched, retry;
+ struct printk_info info;
+ struct printk_record r;
++ u64 seq;
+
+ if (console_suspended) {
+ up_console_sem();
+@@ -2630,12 +2632,14 @@ void console_unlock(void)
+ size_t len;
+
+ skip:
+- if (!prb_read_valid(prb, console_seq, &r))
++ seq = atomic64_read(&console_seq);
++ if (!prb_read_valid(prb, seq, &r))
+ break;
+
+- if (console_seq != r.info->seq) {
+- console_dropped += r.info->seq - console_seq;
+- console_seq = r.info->seq;
++ if (seq != r.info->seq) {
++ console_dropped += r.info->seq - seq;
++ atomic64_set(&console_seq, r.info->seq);
++ seq = r.info->seq;
+ }
+
+ if (suppress_message_printing(r.info->level)) {
+@@ -2644,13 +2648,13 @@ void console_unlock(void)
+ * directly to the console when we received it, and
+ * record that has level above the console loglevel.
+ */
+- console_seq++;
++ atomic64_set(&console_seq, seq + 1);
+ goto skip;
+ }
+
+ /* Output to all consoles once old messages replayed. */
+ if (unlikely(exclusive_console &&
+- console_seq >= exclusive_console_stop_seq)) {
++ seq >= exclusive_console_stop_seq)) {
+ exclusive_console = NULL;
+ }
+
+@@ -2671,7 +2675,7 @@ void console_unlock(void)
+ len = record_print_text(&r,
+ console_msg_format & MSG_FORMAT_SYSLOG,
+ printk_time);
+- console_seq++;
++ atomic64_set(&console_seq, seq + 1);
+
+ /*
+ * While actively printing out messages, if another printk()
+@@ -2702,7 +2706,7 @@ void console_unlock(void)
+ * there's a new owner and the console_unlock() from them will do the
+ * flush, no worries.
+ */
+- retry = prb_read_valid(prb, console_seq, NULL);
++ retry = prb_read_valid(prb, atomic64_read(&console_seq), NULL);
+ if (retry && console_trylock())
+ goto again;
+ }
+@@ -2765,7 +2769,7 @@ void console_flush_on_panic(enum con_flush_mode mode)
+ console_may_schedule = 0;
+
+ if (mode == CONSOLE_REPLAY_ALL)
+- console_seq = prb_first_valid_seq(prb);
++ atomic64_set(&console_seq, prb_first_valid_seq(prb));
+ console_unlock();
+ }
+
+@@ -3002,11 +3006,11 @@ void register_console(struct console *newcon)
+ * ignores console_lock.
+ */
+ exclusive_console = newcon;
+- exclusive_console_stop_seq = console_seq;
++ exclusive_console_stop_seq = atomic64_read(&console_seq);
+
+ /* Get a consistent copy of @syslog_seq. */
+ spin_lock_irqsave(&syslog_lock, flags);
+- console_seq = syslog_seq;
++ atomic64_set(&console_seq, syslog_seq);
+ spin_unlock_irqrestore(&syslog_lock, flags);
+ }
+ console_unlock();
+--
+2.43.0
+