Messages in this thread | | | Date | Tue, 11 Jan 2022 14:53:04 +0000 | From | Chris Down <> | Subject | Re: [RFC 1/2] printk/dynamic_debug: Remove cyclic dependency between printk.h and dynamic_debug.h |
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Hey Petr,
Petr Mladek writes: >`make headerdep` reports many circular dependencies with the same >pattern: > >In file included from linux/printk.h, > from linux/dynamic_debug.h:188 > from linux/printk.h:559 <-- here > >It looks like false positive: > > + printk.h includes dynamic_debug.h when CONFIG_DYNAMIC_DEBUG_CORE > + dynamic_debug.h includes printk.h when !CONFIG_DYNAMIC_DEBUG_CORE > >Anyway, it would be great to get rid of this dependency because it is >tricky and it might hit us in the future. Also it might hide another >more complicated cyclic dependencies.
Sounds reasonable.
>One solution would be to move the inlined ddebug_dyndbg_module_param_cb() >and dynamic_debug_exec_queries() from 'dynamic_debug.h' into some .c so >that it will not be needed to inline printk() in 'dynamic_debug.h'. > >The obvious location would be 'lib/dynamic_debug.c'. But it is built >only when CONFIG_DYNAMIC_DEBUG_CORE is set. And the problematic >inline variants are used only when this config option is _not_ set. >So that it is not that easy. > >Instead, this patch adds 'include/linux/printk_core.h' and moves some >lowlevel printk API there. Then the raw _printk() can be called from >the inlined code in 'dynamic_debug.h'. > >Note that it is not enough to declare _printk() in 'dynamic_debug.h'. >It would break build with CONFIG_PRINTK where it is an inlined nope.
s/nope/nop/, and you mean !CONFIG_PRINTK instead of CONFIG_PRINTK. Or did I misunderstand?
> >The drawback of this approach is that _printk() does not add metadata for >printk indexing and the message is not listed in <debugfs>/printk/index/. >But it should be acceptable here. The strings are used only for debugging.
Agreed that these are fine to omit from a printk indexing perspective.
>The advantage is that this approach might be used to solve other cyclic >dependencies, for example in bug.h. > >Reported-by: Andy Shevchenko <andy.shevchenko@gmail.com> >Signed-off-by: Petr Mladek <pmladek@suse.com>
Thanks! Looks good to me with changelog fixes.
Acked-by: Chris Down <chris@chrisdown.name>
>--- > MAINTAINERS | 1 + > include/linux/dynamic_debug.h | 10 ++--- > include/linux/printk.h | 57 +------------------------- > include/linux/printk_core.h | 76 +++++++++++++++++++++++++++++++++++ > 4 files changed, 83 insertions(+), 61 deletions(-) > create mode 100644 include/linux/printk_core.h > >diff --git a/MAINTAINERS b/MAINTAINERS >index fb18ce7168aa..eadb77da01db 100644 >--- a/MAINTAINERS >+++ b/MAINTAINERS >@@ -15340,6 +15340,7 @@ R: Steven Rostedt <rostedt@goodmis.org> > R: John Ogness <john.ogness@linutronix.de> > S: Maintained > F: include/linux/printk.h >+F: include/linux/printk_core.h > F: kernel/printk/ > > PRINTK INDEXING >diff --git a/include/linux/dynamic_debug.h b/include/linux/dynamic_debug.h >index dce631e678dd..63f6ebd6a14c 100644 >--- a/include/linux/dynamic_debug.h >+++ b/include/linux/dynamic_debug.h >@@ -185,7 +185,7 @@ void __dynamic_ibdev_dbg(struct _ddebug *descriptor, > > #include <linux/string.h> > #include <linux/errno.h> >-#include <linux/printk.h> >+#include <linux/printk_core.h> > > static inline int ddebug_add_module(struct _ddebug *tab, unsigned int n, > const char *modname) >@@ -202,9 +202,8 @@ static inline int ddebug_dyndbg_module_param_cb(char *param, char *val, > const char *modname) > { > if (strstr(param, "dyndbg")) { >- /* avoid pr_warn(), which wants pr_fmt() fully defined */ >- printk(KERN_WARNING "dyndbg param is supported only in " >- "CONFIG_DYNAMIC_DEBUG builds\n"); >+ /* Use raw _printk() to avoid cyclic dependency. */ >+ _printk(KERN_WARNING "dyndbg param is supported only in CONFIG_DYNAMIC_DEBUG builds\n"); > return 0; /* allow and ignore */ > } > return -EINVAL; >@@ -223,7 +222,8 @@ static inline int ddebug_dyndbg_module_param_cb(char *param, char *val, > > static inline int dynamic_debug_exec_queries(const char *query, const char *modname) > { >- pr_warn("kernel not built with CONFIG_DYNAMIC_DEBUG_CORE\n"); >+ /* Use raw _printk() to avoid cyclic dependency. */ >+ _printk(KERN_WARNING "kernel not built with CONFIG_DYNAMIC_DEBUG_CORE\n"); > return 0; > } > >diff --git a/include/linux/printk.h b/include/linux/printk.h >index 9497f6b98339..c20f55df7fa6 100644 >--- a/include/linux/printk.h >+++ b/include/linux/printk.h >@@ -5,6 +5,7 @@ > #include <linux/stdarg.h> > #include <linux/init.h> > #include <linux/kern_levels.h> >+#include <linux/printk_core.h> > #include <linux/linkage.h> > #include <linux/cache.h> > #include <linux/ratelimit_types.h> >@@ -144,32 +145,6 @@ void early_printk(const char *s, ...) { } > struct dev_printk_info; > > #ifdef CONFIG_PRINTK >-asmlinkage __printf(4, 0) >-int vprintk_emit(int facility, int level, >- const struct dev_printk_info *dev_info, >- const char *fmt, va_list args); >- >-asmlinkage __printf(1, 0) >-int vprintk(const char *fmt, va_list args); >- >-asmlinkage __printf(1, 2) __cold >-int _printk(const char *fmt, ...); >- >-/* >- * Special printk facility for scheduler/timekeeping use only, _DO_NOT_USE_ ! >- */ >-__printf(1, 2) __cold int _printk_deferred(const char *fmt, ...); >- >-extern void __printk_safe_enter(void); >-extern void __printk_safe_exit(void); >-/* >- * The printk_deferred_enter/exit macros are available only as a hack for >- * some code paths that need to defer all printk console printing. Interrupts >- * must be disabled for the deferred duration. >- */ >-#define printk_deferred_enter __printk_safe_enter >-#define printk_deferred_exit __printk_safe_exit >- > /* > * Please don't use printk_ratelimit(), because it shares ratelimiting state > * with all other unrelated printk_ratelimit() callsites. Instead use >@@ -189,7 +164,6 @@ devkmsg_sysctl_set_loglvl(struct ctl_table *table, int write, void *buf, > > extern void wake_up_klogd(void); > >-char *log_buf_addr_get(void); > u32 log_buf_len_get(void); > void log_buf_vmcoreinfo_setup(void); > void __init setup_log_buf(int early); >@@ -200,30 +174,6 @@ extern asmlinkage void dump_stack_lvl(const char *log_lvl) __cold; > extern asmlinkage void dump_stack(void) __cold; > void printk_trigger_flush(void); > #else >-static inline __printf(1, 0) >-int vprintk(const char *s, va_list args) >-{ >- return 0; >-} >-static inline __printf(1, 2) __cold >-int _printk(const char *s, ...) >-{ >- return 0; >-} >-static inline __printf(1, 2) __cold >-int _printk_deferred(const char *s, ...) >-{ >- return 0; >-} >- >-static inline void printk_deferred_enter(void) >-{ >-} >- >-static inline void printk_deferred_exit(void) >-{ >-} >- > static inline int printk_ratelimit(void) > { > return 0; >@@ -238,11 +188,6 @@ static inline void wake_up_klogd(void) > { > } > >-static inline char *log_buf_addr_get(void) >-{ >- return NULL; >-} >- > static inline u32 log_buf_len_get(void) > { > return 0; >diff --git a/include/linux/printk_core.h b/include/linux/printk_core.h >new file mode 100644 >index 000000000000..a2b8727a2873 >--- /dev/null >+++ b/include/linux/printk_core.h >@@ -0,0 +1,76 @@ >+/* SPDX-License-Identifier: GPL-2.0 */ >+#ifndef __KERNEL_PRINTK_CORE__ >+#define __KERNEL_PRINTK_CORE__ >+ >+#include <linux/stdarg.h> >+#include <linux/kern_levels.h> >+#include <linux/linkage.h> >+ >+/* Low level printk API. Use carefully! */ >+ >+#ifdef CONFIG_PRINTK >+ >+struct dev_printk_info; >+ >+asmlinkage __printf(4, 0) >+int vprintk_emit(int facility, int level, >+ const struct dev_printk_info *dev_info, >+ const char *fmt, va_list args); >+ >+asmlinkage __printf(1, 0) >+int vprintk(const char *fmt, va_list args); >+ >+asmlinkage __printf(1, 2) __cold >+int _printk(const char *fmt, ...); >+ >+/* >+ * Special printk facility for scheduler/timekeeping use only, _DO_NOT_USE_ ! >+ */ >+__printf(1, 2) __cold int _printk_deferred(const char *fmt, ...); >+ >+extern void __printk_safe_enter(void); >+extern void __printk_safe_exit(void); >+/* >+ * The printk_deferred_enter/exit macros are available only as a hack for >+ * some code paths that need to defer all printk console printing. Interrupts >+ * must be disabled for the deferred duration. >+ */ >+#define printk_deferred_enter __printk_safe_enter >+#define printk_deferred_exit __printk_safe_exit >+ >+char *log_buf_addr_get(void); >+ >+#else /* CONFIG_PRINTK */ >+ >+static inline __printf(1, 0) >+int vprintk(const char *s, va_list args) >+{ >+ return 0; >+} >+static inline __printf(1, 2) __cold >+int _printk(const char *s, ...) >+{ >+ return 0; >+} >+static inline __printf(1, 2) __cold >+int _printk_deferred(const char *s, ...) >+{ >+ return 0; >+} >+ >+static inline void printk_deferred_enter(void) >+{ >+} >+ >+static inline void printk_deferred_exit(void) >+{ >+} >+ >+static inline char *log_buf_addr_get(void) >+{ >+ return NULL; >+} >+ >+#endif /* CONFING_PRINTK */ >+ >+#endif >-- >2.26.2 >
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