linux-kernel - [PATCH printk v2 2/4] printk: Add this_cpu_in

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Message-Id: <20231013204340.1112036-3-john.ogness@linutronix.de>
Date:   Fri, 13 Oct 2023 22:49:38 +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 v2 2/4] printk: Add this_cpu_in_panic()

There is already panic_in_progress() and other_cpu_in_panic(),
but checking if the current CPU is the panic CPU must still be
open coded.

Add this_cpu_in_panic() to complete the set.

Signed-off-by: John Ogness <john.ogness@...utronix.de>
---
 kernel/printk/internal.h |  1 +
 kernel/printk/printk.c   | 43 +++++++++++++++++++++-------------------
 2 files changed, 24 insertions(+), 20 deletions(-)

diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h
index 7d4979d5c3ce..2397734c0fd2 100644
--- a/kernel/printk/internal.h
+++ b/kernel/printk/internal.h
@@ -105,3 +105,4 @@ struct printk_message {
 };
 
 bool other_cpu_in_panic(void);
+bool this_cpu_in_panic(void);
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index abb6a50ee26f..19b752880879 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -351,6 +351,29 @@ static bool panic_in_progress(void)
 	return unlikely(atomic_read(&panic_cpu) != PANIC_CPU_INVALID);
 }
 
+/* Return true if a panic is in progress on the current CPU. */
+bool this_cpu_in_panic(void)
+{
+	/*
+	 * We can use raw_smp_processor_id() here because it is impossible for
+	 * the task to be migrated to the panic_cpu, or away from it. If
+	 * panic_cpu has already been set, and we're not currently executing on
+	 * that CPU, then we never will be.
+	 */
+	return unlikely(atomic_read(&panic_cpu) == raw_smp_processor_id());
+}
+
+/*
+ * Return true if a panic is in progress on a remote CPU.
+ *
+ * On true, the local CPU should immediately release any printing resources
+ * that may be needed by the panic CPU.
+ */
+bool other_cpu_in_panic(void)
+{
+	return (panic_in_progress() && !this_cpu_in_panic());
+}
+
 /*
  * This is used for debugging the mess that is the VT code by
  * keeping track if we have the console semaphore held. It's
@@ -2610,26 +2633,6 @@ static int console_cpu_notify(unsigned int cpu)
 	return 0;
 }
 
-/*
- * Return true if a panic is in progress on a remote CPU.
- *
- * On true, the local CPU should immediately release any printing resources
- * that may be needed by the panic CPU.
- */
-bool other_cpu_in_panic(void)
-{
-	if (!panic_in_progress())
-		return false;
-
-	/*
-	 * We can use raw_smp_processor_id() here because it is impossible for
-	 * the task to be migrated to the panic_cpu, or away from it. If
-	 * panic_cpu has already been set, and we're not currently executing on
-	 * that CPU, then we never will be.
-	 */
-	return atomic_read(&panic_cpu) != raw_smp_processor_id();
-}
-
 /**
  * console_lock - block the console subsystem from printing
  *
-- 
2.39.2