once: implement DO_ONCE_LITE for non-fast-path "do once" functionality

Certain uses of "do once" functionality reside outside of fast path,
and so do not require jump label patching via static keys, making
existing DO_ONCE undesirable in such cases.

Replace uses of __section(".data.once") with DO_ONCE_LITE(_IF)?

This patch changes the return values of xfs_printk_once, printk_once,
and printk_deferred_once. Before, they returned whether the print was
performed, but now, they always return true. This is okay because the
return values of the following macros are entirely ignored throughout
the kernel:
- xfs_printk_once
- xfs_warn_once
- xfs_notice_once
- xfs_info_once
- printk_once
- pr_emerg_once
- pr_alert_once
- pr_crit_once
- pr_err_once
- pr_warn_once
- pr_notice_once
- pr_info_once
- pr_devel_once
- pr_debug_once
- printk_deferred_once
- orc_warn

Changes
v3:
  - Expand commit message to explain why changing return values of
    xfs_printk_once, printk_once, printk_deferred_once is benign
v2:
  - Fix i386 build warnings

Signed-off-by: Tanner Love <tannerlove@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Acked-by: Mahesh Bandewar <maheshb@google.com>
Acked-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/fs/xfs/xfs_message.h b/fs/xfs/xfs_message.h
index 7ec1a9207517f85a0b99af23fd238c59615d9e18..bb9860ec9a9346610588679de69e53be98ee7371 100644 (file)
--- a/fs/xfs/xfs_message.h
+++ b/fs/xfs/xfs_message.h
@@ -2,6 +2,8 @@
 #ifndef __XFS_MESSAGE_H
 #define __XFS_MESSAGE_H 1
 
+#include <linux/once_lite.h>
+
 struct xfs_mount;
 
 extern __printf(2, 3)
@@ -41,16 +43,7 @@ do {                                                                 \
 } while (0)
 
 #define xfs_printk_once(func, dev, fmt, ...)                   \
-({                                                             \
-       static bool __section(".data.once") __print_once;       \
-       bool __ret_print_once = !__print_once;                  \
-                                                               \
-       if (!__print_once) {                                    \
-               __print_once = true;                            \
-               func(dev, fmt, ##__VA_ARGS__);                  \
-       }                                                       \
-       unlikely(__ret_print_once);                             \
-})
+       DO_ONCE_LITE(func, dev, fmt, ##__VA_ARGS__)
 
 #define xfs_emerg_ratelimited(dev, fmt, ...)                           \
        xfs_printk_ratelimited(xfs_emerg, dev, fmt, ##__VA_ARGS__)

diff --git a/include/asm-generic/bug.h b/include/asm-generic/bug.h
index b402494883b682e8d0fdea0a702a37ee93078632..bafc51f483c49ab808e5c2dc75ee148c8d405e4f 100644 (file)
--- a/include/asm-generic/bug.h
+++ b/include/asm-generic/bug.h
@@ -4,6 +4,7 @@
 
 #include <linux/compiler.h>
 #include <linux/instrumentation.h>
+#include <linux/once_lite.h>
 
 #define CUT_HERE               "------------[ cut here ]------------\n"
 
@@ -140,39 +141,15 @@ void __warn(const char *file, int line, void *caller, unsigned taint,
 })
 
 #ifndef WARN_ON_ONCE
-#define WARN_ON_ONCE(condition)        ({                              \
-       static bool __section(".data.once") __warned;           \
-       int __ret_warn_once = !!(condition);                    \
-                                                               \
-       if (unlikely(__ret_warn_once && !__warned)) {           \
-               __warned = true;                                \
-               WARN_ON(1);                                     \
-       }                                                       \
-       unlikely(__ret_warn_once);                              \
-})
+#define WARN_ON_ONCE(condition)                                        \
+       DO_ONCE_LITE_IF(condition, WARN_ON, 1)
 #endif
 
-#define WARN_ONCE(condition, format...)        ({                      \
-       static bool __section(".data.once") __warned;           \
-       int __ret_warn_once = !!(condition);                    \
-                                                               \
-       if (unlikely(__ret_warn_once && !__warned)) {           \
-               __warned = true;                                \
-               WARN(1, format);                                \
-       }                                                       \
-       unlikely(__ret_warn_once);                              \
-})
+#define WARN_ONCE(condition, format...)                                \
+       DO_ONCE_LITE_IF(condition, WARN, 1, format)
 
-#define WARN_TAINT_ONCE(condition, taint, format...)   ({      \
-       static bool __section(".data.once") __warned;           \
-       int __ret_warn_once = !!(condition);                    \
-                                                               \
-       if (unlikely(__ret_warn_once && !__warned)) {           \
-               __warned = true;                                \
-               WARN_TAINT(1, taint, format);                   \
-       }                                                       \
-       unlikely(__ret_warn_once);                              \
-})
+#define WARN_TAINT_ONCE(condition, taint, format...)           \
+       DO_ONCE_LITE_IF(condition, WARN_TAINT, 1, taint, format)
 
 #else /* !CONFIG_BUG */
 #ifndef HAVE_ARCH_BUG

diff --git a/include/linux/once_lite.h b/include/linux/once_lite.h
new file mode 100644 (file)
index 0000000..861e606
--- /dev/null
+++ b/include/linux/once_lite.h
@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_ONCE_LITE_H
+#define _LINUX_ONCE_LITE_H
+
+#include <linux/types.h>
+
+/* Call a function once. Similar to DO_ONCE(), but does not use jump label
+ * patching via static keys.
+ */
+#define DO_ONCE_LITE(func, ...)                                                \
+       DO_ONCE_LITE_IF(true, func, ##__VA_ARGS__)
+#define DO_ONCE_LITE_IF(condition, func, ...)                          \
+       ({                                                              \
+               static bool __section(".data.once") __already_done;     \
+               bool __ret_do_once = !!(condition);                     \
+                                                                       \
+               if (unlikely(__ret_do_once && !__already_done)) {       \
+                       __already_done = true;                          \
+                       func(__VA_ARGS__);                              \
+               }                                                       \
+               unlikely(__ret_do_once);                                \
+       })
+
+#endif /* _LINUX_ONCE_LITE_H */

diff --git a/include/linux/printk.h b/include/linux/printk.h
index fe7eb2351610d0181caa8c42d0bccaa12bd3f790..885379a1c9a12ddd511f7a8253867718e0cdc2e9 100644 (file)
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -8,6 +8,7 @@
 #include <linux/linkage.h>
 #include <linux/cache.h>
 #include <linux/ratelimit_types.h>
+#include <linux/once_lite.h>
 
 extern const char linux_banner[];
 extern const char linux_proc_banner[];
@@ -436,27 +437,9 @@ extern int kptr_restrict;
 
 #ifdef CONFIG_PRINTK
 #define printk_once(fmt, ...)                                  \
-({                                                             \
-       static bool __section(".data.once") __print_once;       \
-       bool __ret_print_once = !__print_once;                  \
-                                                               \
-       if (!__print_once) {                                    \
-               __print_once = true;                            \
-               printk(fmt, ##__VA_ARGS__);                     \
-       }                                                       \
-       unlikely(__ret_print_once);                             \
-})
+       DO_ONCE_LITE(printk, fmt, ##__VA_ARGS__)
 #define printk_deferred_once(fmt, ...)                         \
-({                                                             \
-       static bool __section(".data.once") __print_once;       \
-       bool __ret_print_once = !__print_once;                  \
-                                                               \
-       if (!__print_once) {                                    \
-               __print_once = true;                            \
-               printk_deferred(fmt, ##__VA_ARGS__);            \
-       }                                                       \
-       unlikely(__ret_print_once);                             \
-})
+       DO_ONCE_LITE(printk_deferred, fmt, ##__VA_ARGS__)
 #else
 #define printk_once(fmt, ...)                                  \
        no_printk(fmt, ##__VA_ARGS__)

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index cd80d046c7a5d413225951ef90746c8c10a44185..d5d8c088a55dbc5a041c2e19b5633d9923cc4ad8 100644 (file)
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -20,6 +20,7 @@
 #include <linux/irq_work.h>
 #include <linux/workqueue.h>
 #include <linux/ctype.h>
+#include <linux/once_lite.h>
 
 #ifdef CONFIG_FTRACE_SYSCALLS
 #include <asm/unistd.h>                /* For NR_SYSCALLS           */
@@ -99,16 +100,8 @@ enum trace_type {
 #include "trace_entries.h"
 
 /* Use this for memory failure errors */
-#define MEM_FAIL(condition, fmt, ...) ({                       \
-       static bool __section(".data.once") __warned;           \
-       int __ret_warn_once = !!(condition);                    \
-                                                               \
-       if (unlikely(__ret_warn_once && !__warned)) {           \
-               __warned = true;                                \
-               pr_err("ERROR: " fmt, ##__VA_ARGS__);           \
-       }                                                       \
-       unlikely(__ret_warn_once);                              \
-})
+#define MEM_FAIL(condition, fmt, ...)                                  \
+       DO_ONCE_LITE_IF(condition, pr_err, "ERROR: " fmt, ##__VA_ARGS__)
 
 /*
  * syscalls are special, and need special handling, this is why