linux-kernel - [RFC PATCH v1 03/25] printk-rb: define ring buffer struct and initializer

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Message-Id: <20190212143003.48446-4-john.ogness@linutronix.de>
Date:   Tue, 12 Feb 2019 15:29:41 +0100
From:   John Ogness <john.ogness@...utronix.de>
To:     linux-kernel@...r.kernel.org
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Daniel Wang <wonderfly@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alan Cox <gnomes@...rguk.ukuu.org.uk>,
        Jiri Slaby <jslaby@...e.com>,
        Peter Feiner <pfeiner@...gle.com>,
        linux-serial@...r.kernel.org,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Subject: [RFC PATCH v1 03/25] printk-rb: define ring buffer struct and initializer

See Documentation/printk-ringbuffer.txt for details about the
initializer arguments.

Signed-off-by: John Ogness <john.ogness@...utronix.de>
---
 include/linux/printk_ringbuffer.h | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/include/linux/printk_ringbuffer.h b/include/linux/printk_ringbuffer.h
index 75f5708ea902..0e6e8dd0d01e 100644
--- a/include/linux/printk_ringbuffer.h
+++ b/include/linux/printk_ringbuffer.h
@@ -10,6 +10,20 @@ struct prb_cpulock {
 	unsigned long __percpu *irqflags;
 };
 
+struct printk_ringbuffer {
+	void *buffer;
+	unsigned int size_bits;
+
+	u64 seq;
+
+	atomic_long_t tail;
+	atomic_long_t head;
+	atomic_long_t reserve;
+
+	struct prb_cpulock *cpulock;
+	atomic_t ctx;
+};
+
 #define DECLARE_STATIC_PRINTKRB_CPULOCK(name)				\
 static DEFINE_PER_CPU(unsigned long, _##name##_percpu_irqflags);	\
 static struct prb_cpulock name = {					\
@@ -17,6 +31,20 @@ static struct prb_cpulock name = {					\
 	.irqflags = &_##name##_percpu_irqflags,				\
 }
 
+#define DECLARE_STATIC_PRINTKRB(name, szbits, cpulockptr)		\
+static char _##name##_buffer[1 << (szbits)]				\
+	__aligned(__alignof__(long));					\
+static struct printk_ringbuffer name = {				\
+	.buffer = &_##name##_buffer[0],					\
+	.size_bits = szbits,						\
+	.seq = 0,							\
+	.tail = ATOMIC_LONG_INIT(-111 * sizeof(long)),			\
+	.head = ATOMIC_LONG_INIT(-111 * sizeof(long)),			\
+	.reserve = ATOMIC_LONG_INIT(-111 * sizeof(long)),		\
+	.cpulock = cpulockptr,						\
+	.ctx = ATOMIC_INIT(0),						\
+}
+
 /* utility functions */
 void prb_lock(struct prb_cpulock *cpu_lock, unsigned int *cpu_store);
 void prb_unlock(struct prb_cpulock *cpu_lock, unsigned int cpu_store);
-- 
2.11.0