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From: John Ogness <john.ogness@linutronix.de>
Date: Mon, 30 Nov 2020 01:42:05 +0106
Subject: [PATCH 16/21] printk: change @console_seq to atomic64_t
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(-)
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -366,12 +366,13 @@ 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];
@@ -2217,7 +2218,7 @@ 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;
@@ -2526,6 +2527,7 @@ 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();
@@ -2569,12 +2571,14 @@ void console_unlock(void)
printk_safe_enter_irqsave(flags);
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)) {
@@ -2583,13 +2587,13 @@ 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;
}
@@ -2610,7 +2614,7 @@ 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()
@@ -2645,7 +2649,7 @@ 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);
printk_safe_exit_irqrestore(flags);
if (retry && console_trylock())
@@ -2710,7 +2714,7 @@ void console_flush_on_panic(enum con_flu
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();
}
@@ -2947,11 +2951,11 @@ void register_console(struct console *ne
* 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();
|
