Function nbcon_context_try_acquire, nbcon_context_relase and
console_is_usable are going to be used in the next patch.
Signed-off-by: Marcos Paulo de Souza <mpdesouza@suse.com>
---
include/linux/console.h | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
kernel/printk/internal.h | 41 -----------------------------------------
kernel/printk/nbcon.c | 4 ++--
3 files changed, 50 insertions(+), 43 deletions(-)
diff --git a/include/linux/console.h b/include/linux/console.h
index 8f10d0a85bb4536e4b0dda4e8ccbdf87978bbb4a..d5398b4be4f7ce8d1642b919952710431b53a8ad 100644
--- a/include/linux/console.h
+++ b/include/linux/console.h
@@ -599,19 +599,67 @@ static inline bool console_is_registered(const struct console *con)
hlist_for_each_entry(con, &console_list, node)
#ifdef CONFIG_PRINTK
+extern bool nbcon_context_try_acquire(struct nbcon_context *ctxt);
+extern void nbcon_context_release(struct nbcon_context *ctxt);
extern void nbcon_cpu_emergency_enter(void);
extern void nbcon_cpu_emergency_exit(void);
extern bool nbcon_can_proceed(struct nbcon_write_context *wctxt);
extern bool nbcon_enter_unsafe(struct nbcon_write_context *wctxt);
extern bool nbcon_exit_unsafe(struct nbcon_write_context *wctxt);
extern void nbcon_reacquire_nobuf(struct nbcon_write_context *wctxt);
+
+/*
+ * Check if the given console is currently capable and allowed to print
+ * records. Note that this function does not consider the current context,
+ * which can also play a role in deciding if @con can be used to print
+ * records.
+ */
+static inline bool console_is_usable(struct console *con, short flags, bool use_atomic)
+{
+ if (!(flags & CON_ENABLED))
+ return false;
+
+ if ((flags & CON_SUSPENDED))
+ return false;
+
+ if (flags & CON_NBCON) {
+ /* The write_atomic() callback is optional. */
+ if (use_atomic && !con->write_atomic)
+ return false;
+
+ /*
+ * For the !use_atomic case, @printk_kthreads_running is not
+ * checked because the write_thread() callback is also used
+ * via the legacy loop when the printer threads are not
+ * available.
+ */
+ } else {
+ if (!con->write)
+ return false;
+ }
+
+ /*
+ * Console drivers may assume that per-cpu resources have been
+ * allocated. So unless they're explicitly marked as being able to
+ * cope (CON_ANYTIME) don't call them until this CPU is officially up.
+ */
+ if (!cpu_online(raw_smp_processor_id()) && !(flags & CON_ANYTIME))
+ return false;
+
+ return true;
+}
+
#else
+static inline bool nbcon_context_try_acquire(struct nbcon_context *ctxt) { }
+static inline void nbcon_context_release(struct nbcon_context *ctxt) { }
static inline void nbcon_cpu_emergency_enter(void) { }
static inline void nbcon_cpu_emergency_exit(void) { }
static inline bool nbcon_can_proceed(struct nbcon_write_context *wctxt) { return false; }
static inline bool nbcon_enter_unsafe(struct nbcon_write_context *wctxt) { return false; }
static inline bool nbcon_exit_unsafe(struct nbcon_write_context *wctxt) { return false; }
static inline void nbcon_reacquire_nobuf(struct nbcon_write_context *wctxt) { }
+static inline bool console_is_usable(struct console *con, short flags,
+ bool use_atomic) { return false; }
#endif
extern int console_set_on_cmdline;
diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h
index 48a24e7b309db20fdd7419f7aeda68ea7c79fd80..4ad51a98690b43fd2383a0c6e70ac4da68c34da3 100644
--- a/kernel/printk/internal.h
+++ b/kernel/printk/internal.h
@@ -112,47 +112,6 @@ bool nbcon_kthread_create(struct console *con);
void nbcon_kthread_stop(struct console *con);
void nbcon_kthreads_wake(void);
-/*
- * Check if the given console is currently capable and allowed to print
- * records. Note that this function does not consider the current context,
- * which can also play a role in deciding if @con can be used to print
- * records.
- */
-static inline bool console_is_usable(struct console *con, short flags, bool use_atomic)
-{
- if (!(flags & CON_ENABLED))
- return false;
-
- if ((flags & CON_SUSPENDED))
- return false;
-
- if (flags & CON_NBCON) {
- /* The write_atomic() callback is optional. */
- if (use_atomic && !con->write_atomic)
- return false;
-
- /*
- * For the !use_atomic case, @printk_kthreads_running is not
- * checked because the write_thread() callback is also used
- * via the legacy loop when the printer threads are not
- * available.
- */
- } else {
- if (!con->write)
- return false;
- }
-
- /*
- * Console drivers may assume that per-cpu resources have been
- * allocated. So unless they're explicitly marked as being able to
- * cope (CON_ANYTIME) don't call them until this CPU is officially up.
- */
- if (!cpu_online(raw_smp_processor_id()) && !(flags & CON_ANYTIME))
- return false;
-
- return true;
-}
-
/**
* nbcon_kthread_wake - Wake up a console printing thread
* @con: Console to operate on
diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c
index fd12efcc4aeda8883773d9807bc215f6e5cdf71a..b95030018472493b1019932c3d1d92c1abd044ee 100644
--- a/kernel/printk/nbcon.c
+++ b/kernel/printk/nbcon.c
@@ -568,7 +568,7 @@ static struct printk_buffers panic_nbcon_pbufs;
* in an unsafe state. Otherwise, on success the caller may assume
* the console is not in an unsafe state.
*/
-static bool nbcon_context_try_acquire(struct nbcon_context *ctxt)
+bool nbcon_context_try_acquire(struct nbcon_context *ctxt)
{
unsigned int cpu = smp_processor_id();
struct console *con = ctxt->console;
@@ -648,7 +648,7 @@ static bool nbcon_owner_matches(struct nbcon_state *cur, int expected_cpu,
* nbcon_context_release - Release the console
* @ctxt: The nbcon context from nbcon_context_try_acquire()
*/
-static void nbcon_context_release(struct nbcon_context *ctxt)
+void nbcon_context_release(struct nbcon_context *ctxt)
{
unsigned int cpu = smp_processor_id();
struct console *con = ctxt->console;
--
2.50.0On 2025-07-13, Marcos Paulo de Souza <mpdesouza@suse.com> wrote: > Function nbcon_context_try_acquire, nbcon_context_relase and > console_is_usable are going to be used in the next patch. The nbcon_context is supposed is not meant to be exposed like this. I would prefer creating a proper interface rather than having kdb code directly modifying internal structures. I will provide more details in the response to the 2nd patch of this series. John Ogness
Hi Marcos,
kernel test robot noticed the following build errors:
[auto build test ERROR on d0b3b7b22dfa1f4b515fd3a295b3fd958f9e81af]
url: https://github.com/intel-lab-lkp/linux/commits/Marcos-Paulo-de-Souza/printk-nbcon-Export-console_is_usage-and-other-nbcon-symbols/20250713-131106
base: d0b3b7b22dfa1f4b515fd3a295b3fd958f9e81af
patch link: https://lore.kernel.org/r/20250713-nbcon-kgdboc-v1-1-51eccd9247a8%40suse.com
patch subject: [PATCH 1/2] printk: nbcon: Export console_is_usage and other nbcon symbols
config: i386-buildonly-randconfig-004-20250713 (https://download.01.org/0day-ci/archive/20250713/202507131412.Lfp8uefP-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14+deb12u1) 12.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250713/202507131412.Lfp8uefP-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202507131412.Lfp8uefP-lkp@intel.com/
All error/warnings (new ones prefixed by >>):
In file included from kernel/panic.c:32:
include/linux/console.h: In function 'nbcon_context_try_acquire':
>> include/linux/console.h:653:53: warning: no return statement in function returning non-void [-Wreturn-type]
653 | static inline bool nbcon_context_try_acquire(struct nbcon_context *ctxt) { }
| ^~~~~~~~~~~~~
--
In file included from kernel/printk/printk.c:26:
include/linux/console.h: In function 'nbcon_context_try_acquire':
>> include/linux/console.h:653:53: warning: no return statement in function returning non-void [-Wreturn-type]
653 | static inline bool nbcon_context_try_acquire(struct nbcon_context *ctxt) { }
| ^~~~~~~~~~~~~
In file included from kernel/printk/printk.c:62:
kernel/printk/internal.h: At top level:
>> kernel/printk/internal.h:165:20: error: redefinition of 'console_is_usable'
165 | static inline bool console_is_usable(struct console *con, short flags,
| ^~~~~~~~~~~~~~~~~
include/linux/console.h:661:20: note: previous definition of 'console_is_usable' with type 'bool(struct console *, short int, bool)' {aka '_Bool(struct console *, short int, _Bool)'}
661 | static inline bool console_is_usable(struct console *con, short flags,
| ^~~~~~~~~~~~~~~~~
vim +/console_is_usable +165 kernel/printk/internal.h
6b93bb41f6eaa1 Thomas Gleixner 2023-09-16 164
6cb58cfebb2932 John Ogness 2024-09-04 @165 static inline bool console_is_usable(struct console *con, short flags,
6cb58cfebb2932 John Ogness 2024-09-04 166 bool use_atomic) { return false; }
864c25c83d834b John Ogness 2024-08-20 167
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
Hi Marcos,
kernel test robot noticed the following build warnings:
[auto build test WARNING on d0b3b7b22dfa1f4b515fd3a295b3fd958f9e81af]
url: https://github.com/intel-lab-lkp/linux/commits/Marcos-Paulo-de-Souza/printk-nbcon-Export-console_is_usage-and-other-nbcon-symbols/20250713-131106
base: d0b3b7b22dfa1f4b515fd3a295b3fd958f9e81af
patch link: https://lore.kernel.org/r/20250713-nbcon-kgdboc-v1-1-51eccd9247a8%40suse.com
patch subject: [PATCH 1/2] printk: nbcon: Export console_is_usage and other nbcon symbols
config: x86_64-buildonly-randconfig-001-20250713 (https://download.01.org/0day-ci/archive/20250713/202507131443.p6jEjXFw-lkp@intel.com/config)
compiler: clang version 20.1.8 (https://github.com/llvm/llvm-project 87f0227cb60147a26a1eeb4fb06e3b505e9c7261)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250713/202507131443.p6jEjXFw-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202507131443.p6jEjXFw-lkp@intel.com/
All warnings (new ones prefixed by >>):
In file included from drivers/char/tpm/tpm_tis.c:21:
In file included from include/linux/pnp.h:16:
>> include/linux/console.h:653:76: warning: non-void function does not return a value [-Wreturn-type]
653 | static inline bool nbcon_context_try_acquire(struct nbcon_context *ctxt) { }
| ^
In file included from drivers/char/tpm/tpm_tis.c:29:
In file included from drivers/char/tpm/tpm.h:28:
include/linux/tpm_eventlog.h:167:6: warning: variable 'mapping_size' set but not used [-Wunused-but-set-variable]
167 | int mapping_size;
| ^
2 warnings generated.
vim +653 include/linux/console.h
651
652 #else
> 653 static inline bool nbcon_context_try_acquire(struct nbcon_context *ctxt) { }
654 static inline void nbcon_context_release(struct nbcon_context *ctxt) { }
655 static inline void nbcon_cpu_emergency_enter(void) { }
656 static inline void nbcon_cpu_emergency_exit(void) { }
657 static inline bool nbcon_can_proceed(struct nbcon_write_context *wctxt) { return false; }
658 static inline bool nbcon_enter_unsafe(struct nbcon_write_context *wctxt) { return false; }
659 static inline bool nbcon_exit_unsafe(struct nbcon_write_context *wctxt) { return false; }
660 static inline void nbcon_reacquire_nobuf(struct nbcon_write_context *wctxt) { }
661 static inline bool console_is_usable(struct console *con, short flags,
662 bool use_atomic) { return false; }
663 #endif
664
--
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