linux-kernel - [PATCH printk v3 06/15] printk: get caller

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Date:   Wed, 20 Apr 2022 01:52:28 +0206
From:   John Ogness <john.ogness@...utronix.de>
To:     Petr Mladek <pmladek@...e.com>
Cc:     Sergey Senozhatsky <senozhatsky@...omium.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org
Subject: [PATCH printk v3 06/15] printk: get caller_id/timestamp after migration disable

Currently the local CPU timestamp and caller_id for the record are
collected while migration is enabled. Since this information is
CPU-specific, it should be collected with migration disabled.

Migration is disabled immediately after collecting this information
anyway, so just move the information collection to after the
migration disabling.

Signed-off-by: John Ogness <john.ogness@...utronix.de>
Reviewed-by: Sergey Senozhatsky <senozhatsky@...omium.org>
Reviewed-by: Petr Mladek <pmladek@...e.com>
---
 kernel/printk/printk.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 7bb148a1debb..82ad3d3d0d4a 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2063,7 +2063,7 @@ static inline void printk_delay(void)
 static inline u32 printk_caller_id(void)
 {
 	return in_task() ? task_pid_nr(current) :
-		0x80000000 + raw_smp_processor_id();
+		0x80000000 + smp_processor_id();
 }
 
 /**
@@ -2145,7 +2145,6 @@ int vprintk_store(int facility, int level,
 		  const struct dev_printk_info *dev_info,
 		  const char *fmt, va_list args)
 {
-	const u32 caller_id = printk_caller_id();
 	struct prb_reserved_entry e;
 	enum printk_info_flags flags = 0;
 	struct printk_record r;
@@ -2155,10 +2154,14 @@ int vprintk_store(int facility, int level,
 	u8 *recursion_ptr;
 	u16 reserve_size;
 	va_list args2;
+	u32 caller_id;
 	u16 text_len;
 	int ret = 0;
 	u64 ts_nsec;
 
+	if (!printk_enter_irqsave(recursion_ptr, irqflags))
+		return 0;
+
 	/*
 	 * Since the duration of printk() can vary depending on the message
 	 * and state of the ringbuffer, grab the timestamp now so that it is
@@ -2167,8 +2170,7 @@ int vprintk_store(int facility, int level,
 	 */
 	ts_nsec = local_clock();
 
-	if (!printk_enter_irqsave(recursion_ptr, irqflags))
-		return 0;
+	caller_id = printk_caller_id();
 
 	/*
 	 * The sprintf needs to come first since the syslog prefix might be
-- 
2.30.2