linux-kernel - [PATCH v5 3/4] Revert "printk: lock/unlock console only for new logbuf entries"

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Message-Id: <20200709132344.760-4-john.ogness@linutronix.de>
Date:   Thu,  9 Jul 2020 15:29:43 +0206
From:   John Ogness <john.ogness@...utronix.de>
To:     Petr Mladek <pmladek@...e.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrea Parri <parri.andrea@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Paul McKenney <paulmck@...nel.org>, kexec@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v5 3/4] Revert "printk: lock/unlock console only for new logbuf entries"

This reverts commit 3ac37a93fa9217e576bebfd4ba3e80edaaeb2289.

This optimization will not apply once the transition to a lockless
printk is complete. Rather than porting this optimization through
the transition only to remove it anyway, just revert it now to
simplify the transition.

Signed-off-by: John Ogness <john.ogness@...utronix.de>
Acked-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Reviewed-by: Petr Mladek <pmladek@...e.com>
---
 kernel/printk/printk.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index b71eaf5f5a86..1b41e1b98221 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -1981,9 +1981,8 @@ asmlinkage int vprintk_emit(int facility, int level,
 			    const char *fmt, va_list args)
 {
 	int printed_len;
-	bool in_sched = false, pending_output;
+	bool in_sched = false;
 	unsigned long flags;
-	u64 curr_log_seq;
 
 	/* Suppress unimportant messages after panic happens */
 	if (unlikely(suppress_printk))
@@ -1999,13 +1998,11 @@ asmlinkage int vprintk_emit(int facility, int level,
 
 	/* This stops the holder of console_sem just where we want him */
 	logbuf_lock_irqsave(flags);
-	curr_log_seq = log_next_seq;
 	printed_len = vprintk_store(facility, level, dict, dictlen, fmt, args);
-	pending_output = (curr_log_seq != log_next_seq);
 	logbuf_unlock_irqrestore(flags);
 
 	/* If called from the scheduler, we can not call up(). */
-	if (!in_sched && pending_output) {
+	if (!in_sched) {
 		/*
 		 * Disable preemption to avoid being preempted while holding
 		 * console_sem which would prevent anyone from printing to
@@ -2022,8 +2019,7 @@ asmlinkage int vprintk_emit(int facility, int level,
 		preempt_enable();
 	}
 
-	if (pending_output)
-		wake_up_klogd();
+	wake_up_klogd();
 	return printed_len;
 }
 EXPORT_SYMBOL(vprintk_emit);
-- 
2.20.1