From 7b6f9a34e7c1a5c1ffdffcd59b9efdcb465a6e4f Mon Sep 17 00:00:00 2001 From: John Ogness 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-5.10.215-rt107.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 Signed-off-by: Sebastian Andrzej Siewior --- 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 d7f17b8253cdc..818c17b26bdee 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]; @@ -2279,7 +2280,7 @@ 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; @@ -2594,6 +2595,7 @@ 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(); @@ -2636,12 +2638,14 @@ 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)) { @@ -2650,13 +2654,13 @@ 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; } @@ -2677,7 +2681,7 @@ 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() @@ -2708,7 +2712,7 @@ 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; } @@ -2771,7 +2775,7 @@ 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(); } @@ -3031,11 +3035,11 @@ 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(); -- 2.44.0