Date:   Tue, 12 Feb 2019 15:30:03 +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 25/25] printk: remove unused code

Code relating to the safe context and anything dealing with the
previous log buffer implementation is no longer in use. Remove it.

Signed-off-by: John Ogness <john.ogness@...utronix.de>
---
 kernel/printk/internal.h |  53 ---------------
 kernel/printk/printk.c   | 167 ++++-------------------------------------------
 lib/bust_spinlocks.c     |   3 +-
 3 files changed, 13 insertions(+), 210 deletions(-)
 delete mode 100644 kernel/printk/internal.h

diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h
deleted file mode 100644
index 59ad43dba837..000000000000
--- a/kernel/printk/internal.h
+++ /dev/null
@@ -1,53 +0,0 @@
-/*
- * internal.h - printk internal definitions
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License
- * as published by the Free Software Foundation; either version 2
- * of the License, or (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, see <http://www.gnu.org/licenses/>.
- */
-#include <linux/percpu.h>
-
-#ifdef CONFIG_PRINTK
-
-#define PRINTK_SAFE_CONTEXT_MASK	 0x3fffffff
-#define PRINTK_NMI_DIRECT_CONTEXT_MASK	 0x40000000
-#define PRINTK_NMI_CONTEXT_MASK		 0x80000000
-
-extern raw_spinlock_t logbuf_lock;
-
-__printf(5, 0)
-int vprintk_store(int facility, int level,
-		  const char *dict, size_t dictlen,
-		  const char *fmt, va_list args);
-
-__printf(1, 0) int vprintk_default(const char *fmt, va_list args);
-__printf(1, 0) int vprintk_deferred(const char *fmt, va_list args);
-__printf(1, 0) int vprintk_func(const char *fmt, va_list args);
-
-void defer_console_output(void);
-
-#else
-
-__printf(1, 0) int vprintk_func(const char *fmt, va_list args) { return 0; }
-
-/*
- * In !PRINTK builds we still export logbuf_lock spin_lock, console_sem
- * semaphore and some of console functions (console_unlock()/etc.), so
- * printk-safe must preserve the existing local IRQ guarantees.
- */
-#endif /* CONFIG_PRINTK */
-
-#define printk_safe_enter_irqsave(flags) local_irq_save(flags)
-#define printk_safe_exit_irqrestore(flags) local_irq_restore(flags)
-
-#define printk_safe_enter_irq() local_irq_disable()
-#define printk_safe_exit_irq() local_irq_enable()
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 6d5bb7f5f584..8ef35c398887 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -60,7 +60,6 @@
 
 #include "console_cmdline.h"
 #include "braille.h"
-#include "internal.h"
 
 int console_printk[5] = {
 	CONSOLE_LOGLEVEL_DEFAULT,	/* console_loglevel */
@@ -346,41 +345,6 @@ __packed __aligned(4)
 #endif
 ;
 
-/*
- * The logbuf_lock protects kmsg buffer, indices, counters.  This can be taken
- * within the scheduler's rq lock. It must be released before calling
- * console_unlock() or anything else that might wake up a process.
- */
-DEFINE_RAW_SPINLOCK(logbuf_lock);
-
-/*
- * Helper macros to lock/unlock logbuf_lock and switch between
- * printk-safe/unsafe modes.
- */
-#define logbuf_lock_irq()				\
-	do {						\
-		printk_safe_enter_irq();		\
-		raw_spin_lock(&logbuf_lock);		\
-	} while (0)
-
-#define logbuf_unlock_irq()				\
-	do {						\
-		raw_spin_unlock(&logbuf_lock);		\
-		printk_safe_exit_irq();			\
-	} while (0)
-
-#define logbuf_lock_irqsave(flags)			\
-	do {						\
-		printk_safe_enter_irqsave(flags);	\
-		raw_spin_lock(&logbuf_lock);		\
-	} while (0)
-
-#define logbuf_unlock_irqrestore(flags)		\
-	do {						\
-		raw_spin_unlock(&logbuf_lock);		\
-		printk_safe_exit_irqrestore(flags);	\
-	} while (0)
-
 DECLARE_STATIC_PRINTKRB_CPULOCK(printk_cpulock);
 
 #ifdef CONFIG_PRINTK
@@ -390,23 +354,15 @@ DECLARE_STATIC_PRINTKRB(printk_rb, CONFIG_LOG_BUF_SHIFT, &printk_cpulock);
 static DEFINE_MUTEX(syslog_lock);
 DECLARE_STATIC_PRINTKRB_ITER(syslog_iter, &printk_rb);
 
-DECLARE_WAIT_QUEUE_HEAD(log_wait);
-/* the next printk record to read by syslog(READ) or /proc/kmsg */
+/* the last printk record read by syslog(READ) or /proc/kmsg */
 static u64 syslog_seq;
 static size_t syslog_partial;
 static bool syslog_time;
 
-/* index and sequence number of the first record stored in the buffer */
-static u32 log_first_idx;
-
-/* index and sequence number of the next record to store in the buffer */
-static u32 log_next_idx;
-
 static DEFINE_MUTEX(kmsg_dump_lock);
 
-/* the next printk record to read after the last 'clear' command */
+/* the last printk record at the last 'clear' command */
 static u64 clear_seq;
-static u32 clear_idx;
 
 #define PREFIX_MAX		32
 #define LOG_LINE_MAX		(1024 - PREFIX_MAX)
@@ -414,26 +370,6 @@ static u32 clear_idx;
 #define LOG_LEVEL(v)		((v) & 0x07)
 #define LOG_FACILITY(v)		((v) >> 3 & 0xff)
 
-/* record buffer */
-#define LOG_ALIGN __alignof__(struct printk_log)
-#define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
-#define LOG_BUF_LEN_MAX (u32)(1 << 31)
-static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
-static char *log_buf = __log_buf;
-static u32 log_buf_len = __LOG_BUF_LEN;
-
-/* Return log buffer address */
-char *log_buf_addr_get(void)
-{
-	return log_buf;
-}
-
-/* Return log buffer size */
-u32 log_buf_len_get(void)
-{
-	return log_buf_len;
-}
-
 /* human readable text of the record */
 static char *log_text(const struct printk_log *msg)
 {
@@ -944,11 +880,6 @@ const struct file_operations kmsg_fops = {
  */
 void log_buf_vmcoreinfo_setup(void)
 {
-	VMCOREINFO_SYMBOL(log_buf);
-	VMCOREINFO_SYMBOL(log_buf_len);
-	VMCOREINFO_SYMBOL(log_first_idx);
-	VMCOREINFO_SYMBOL(clear_idx);
-	VMCOREINFO_SYMBOL(log_next_idx);
 	/*
 	 * Export struct printk_log size and field offsets. User space tools can
 	 * parse it and detect any changes to structure down the line.
@@ -961,6 +892,8 @@ void log_buf_vmcoreinfo_setup(void)
 }
 #endif
 
+/* FIXME: no support for buffer resizing */
+#if 0
 /* requested log_buf_len from kernel cmdline */
 static unsigned long __initdata new_log_buf_len;
 
@@ -1026,9 +959,12 @@ static void __init log_buf_add_cpu(void)
 #else /* !CONFIG_SMP */
 static inline void log_buf_add_cpu(void) {}
 #endif /* CONFIG_SMP */
+#endif /* 0 */
 
 void __init setup_log_buf(int early)
 {
+/* FIXME: no support for buffer resizing */
+#if 0
 	unsigned long flags;
 	char *new_log_buf;
 	unsigned int free;
@@ -1067,6 +1003,7 @@ void __init setup_log_buf(int early)
 	pr_info("log_buf_len: %u bytes\n", log_buf_len);
 	pr_info("early log buf free: %u(%u%%)\n",
 		free, (free * 100) / __LOG_BUF_LEN);
+#endif
 }
 
 static bool __read_mostly ignore_loglevel;
@@ -2023,31 +1960,6 @@ asmlinkage __visible int printk(const char *fmt, ...)
 	return r;
 }
 EXPORT_SYMBOL(printk);
-
-#else /* CONFIG_PRINTK */
-
-#define LOG_LINE_MAX		0
-#define PREFIX_MAX		0
-#define printk_time		false
-
-static u64 syslog_seq;
-static u32 log_first_idx;
-static char *log_text(const struct printk_log *msg) { return NULL; }
-static char *log_dict(const struct printk_log *msg) { return NULL; }
-static struct printk_log *log_from_idx(u32 idx) { return NULL; }
-static u32 log_next(u32 idx) { return 0; }
-static ssize_t msg_print_ext_header(char *buf, size_t size,
-				    struct printk_log *msg,
-				    u64 seq) { return 0; }
-static ssize_t msg_print_ext_body(char *buf, size_t size,
-				  char *dict, size_t dict_len,
-				  char *text, size_t text_len) { return 0; }
-static void call_console_drivers(u64 seq, const char *ext_text, size_t ext_len,
-				 const char *text, size_t len, int level) {}
-static size_t msg_print_text(const struct printk_log *msg, bool syslog,
-			     bool time, char *buf, size_t size) { return 0; }
-static bool suppress_message_printing(int level) { return false; }
-
 #endif /* CONFIG_PRINTK */
 
 #ifdef CONFIG_EARLY_PRINTK
@@ -2343,15 +2255,10 @@ void console_unblank(void)
 void console_flush_on_panic(void)
 {
 	/*
-	 * If someone else is holding the console lock, trylock will fail
-	 * and may_schedule may be set.  Ignore and proceed to unlock so
-	 * that messages are flushed out.  As this can be called from any
-	 * context and we don't want to get preempted while flushing,
-	 * ensure may_schedule is cleared.
+	 * FIXME: This is currently a NOP. Emergency messages will have been
+	 * printed, but what about if write_atomic is not available on the
+	 * console? What if the printk kthread is still alive?
 	 */
-	console_trylock();
-	console_may_schedule = 0;
-	console_unlock();
 }
 
 /*
@@ -2700,43 +2607,6 @@ static int __init printk_late_init(void)
 late_initcall(printk_late_init);
 
 #if defined CONFIG_PRINTK
-/*
- * Delayed printk version, for scheduler-internal messages:
- */
-#define PRINTK_PENDING_WAKEUP	0x01
-#define PRINTK_PENDING_OUTPUT	0x02
-
-static DEFINE_PER_CPU(int, printk_pending);
-
-static void wake_up_klogd_work_func(struct irq_work *irq_work)
-{
-	int pending = __this_cpu_xchg(printk_pending, 0);
-
-	if (pending & PRINTK_PENDING_OUTPUT) {
-		/* If trylock fails, someone else is doing the printing */
-		if (console_trylock())
-			console_unlock();
-	}
-
-	if (pending & PRINTK_PENDING_WAKEUP)
-		wake_up_interruptible(&log_wait);
-}
-
-static DEFINE_PER_CPU(struct irq_work, wake_up_klogd_work) = {
-	.func = wake_up_klogd_work_func,
-	.flags = IRQ_WORK_LAZY,
-};
-
-void wake_up_klogd(void)
-{
-	preempt_disable();
-	if (waitqueue_active(&log_wait)) {
-		this_cpu_or(printk_pending, PRINTK_PENDING_WAKEUP);
-		irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
-	}
-	preempt_enable();
-}
-
 static int printk_kthread_func(void *data)
 {
 	struct prb_iterator iter;
@@ -2802,22 +2672,9 @@ static int __init init_printk_kthread(void)
 }
 late_initcall(init_printk_kthread);
 
-void defer_console_output(void)
-{
-	preempt_disable();
-	__this_cpu_or(printk_pending, PRINTK_PENDING_OUTPUT);
-	irq_work_queue(this_cpu_ptr(&wake_up_klogd_work));
-	preempt_enable();
-}
-
 int vprintk_deferred(const char *fmt, va_list args)
 {
-	int r;
-
-	r = vprintk_emit(0, LOGLEVEL_SCHED, NULL, 0, fmt, args);
-	defer_console_output();
-
-	return r;
+	return vprintk_emit(0, LOGLEVEL_SCHED, NULL, 0, fmt, args);
 }
 
 int printk_deferred(const char *fmt, ...)
diff --git a/lib/bust_spinlocks.c b/lib/bust_spinlocks.c
index 8be59f84eaea..c6e083323d1b 100644
--- a/lib/bust_spinlocks.c
+++ b/lib/bust_spinlocks.c
@@ -26,7 +26,6 @@ void bust_spinlocks(int yes)
 		unblank_screen();
 #endif
 		console_unblank();
-		if (--oops_in_progress == 0)
-			wake_up_klogd();
+		--oops_in_progress;
 	}
 }
-- 
2.11.0

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