* [PATCH net-next v4 1/5] printk: Add execution context (task name/CPU) to printk_info
2026-01-23 12:17 [PATCH net-next v4 0/5] net: netconsole: convert to NBCON console infrastructure Breno Leitao
@ 2026-01-23 12:17 ` Breno Leitao
2026-01-27 14:58 ` Paolo Abeni
2026-01-27 20:43 ` John Ogness
2026-01-23 12:17 ` [PATCH net-next v4 2/5] netconsole: extract message fragmentation into send_msg_udp() Breno Leitao
` (3 subsequent siblings)
4 siblings, 2 replies; 9+ messages in thread
From: Breno Leitao @ 2026-01-23 12:17 UTC (permalink / raw)
To: Breno Leitao, Andrew Lunn, David S. Miller, Eric Dumazet,
Jakub Kicinski, Paolo Abeni, pmladek, john.ogness
Cc: Greg Kroah-Hartman, Steven Rostedt, Sergey Senozhatsky,
Andrew Morton, netdev, linux-kernel, asantostc, efault, gustavold,
calvin, jv, mpdesouza, kernel-team
Extend struct printk_info to include the task name, pid, and CPU
number where printk messages originate. This information is captured
at vprintk_store() time and propagated through printk_message to
nbcon_write_context, making it available to nbcon console drivers.
This is useful for consoles like netconsole that want to include
execution context in their output, allowing correlation of messages
with specific tasks and CPUs regardless of where the console driver
actually runs.
The feature is controlled by CONFIG_PRINTK_EXECUTION_CTX, which is
automatically selected by CONFIG_NETCONSOLE_DYNAMIC. When disabled,
the helper functions compile to no-ops with no overhead.
Suggested-by: John Ogness <john.ogness@linutronix.de>
Signed-off-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Petr Mladek <pmladek@suse.com>
---
drivers/net/Kconfig | 2 ++
include/linux/console.h | 8 +++++++
kernel/printk/internal.h | 8 +++++++
kernel/printk/nbcon.c | 15 ++++++++++++
kernel/printk/printk.c | 50 ++++++++++++++++++++++++++++++++++++++-
kernel/printk/printk_ringbuffer.h | 5 ++++
lib/Kconfig.debug | 20 ++++++++++++++++
7 files changed, 107 insertions(+), 1 deletion(-)
diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
index 9c7953f8e6377..356c70be868ff 100644
--- a/drivers/net/Kconfig
+++ b/drivers/net/Kconfig
@@ -341,6 +341,8 @@ config NETCONSOLE_DYNAMIC
bool "Dynamic reconfiguration of logging targets"
depends on NETCONSOLE && SYSFS && CONFIGFS_FS && \
!(NETCONSOLE=y && CONFIGFS_FS=m)
+ select PRINTK_EXECUTION_CTX
+ select CONSOLE_HAS_EXECUTION_CTX
help
This option enables the ability to dynamically reconfigure target
parameters (interface, IP addresses, port numbers, MAC addresses)
diff --git a/include/linux/console.h b/include/linux/console.h
index fc9f5c5c1b04c..cc5dc3bf58b60 100644
--- a/include/linux/console.h
+++ b/include/linux/console.h
@@ -298,12 +298,20 @@ struct nbcon_context {
* @outbuf: Pointer to the text buffer for output
* @len: Length to write
* @unsafe_takeover: If a hostile takeover in an unsafe state has occurred
+ * @cpu: CPU on which the message was generated
+ * @pid: PID of the task that generated the message
+ * @comm: Name of the task that generated the message
*/
struct nbcon_write_context {
struct nbcon_context __private ctxt;
char *outbuf;
unsigned int len;
bool unsafe_takeover;
+#ifdef CONFIG_PRINTK_EXECUTION_CTX
+ int cpu;
+ pid_t pid;
+ char comm[TASK_COMM_LEN];
+#endif
};
/**
diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h
index 5f5f626f42794..5fdea56827564 100644
--- a/kernel/printk/internal.h
+++ b/kernel/printk/internal.h
@@ -281,12 +281,20 @@ struct printk_buffers {
* nothing to output and this record should be skipped.
* @seq: The sequence number of the record used for @pbufs->outbuf.
* @dropped: The number of dropped records from reading @seq.
+ * @cpu: CPU on which the message was generated.
+ * @pid: PID of the task that generated the message
+ * @comm: Name of the task that generated the message.
*/
struct printk_message {
struct printk_buffers *pbufs;
unsigned int outbuf_len;
u64 seq;
unsigned long dropped;
+#ifdef CONFIG_PRINTK_EXECUTION_CTX
+ int cpu;
+ pid_t pid;
+ char comm[TASK_COMM_LEN];
+#endif
};
bool printk_get_next_message(struct printk_message *pmsg, u64 seq,
diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c
index 32fc12e536752..391a58be0c5b3 100644
--- a/kernel/printk/nbcon.c
+++ b/kernel/printk/nbcon.c
@@ -946,6 +946,19 @@ void nbcon_reacquire_nobuf(struct nbcon_write_context *wctxt)
}
EXPORT_SYMBOL_GPL(nbcon_reacquire_nobuf);
+#ifdef CONFIG_PRINTK_EXECUTION_CTX
+static void wctxt_load_execution_ctx(struct nbcon_write_context *wctxt,
+ struct printk_message *pmsg)
+{
+ wctxt->cpu = pmsg->cpu;
+ wctxt->pid = pmsg->pid;
+ memcpy(wctxt->comm, pmsg->comm, TASK_COMM_LEN);
+}
+#else
+static void wctxt_load_execution_ctx(struct nbcon_write_context *wctxt,
+ struct printk_message *pmsg) {}
+#endif
+
/**
* nbcon_emit_next_record - Emit a record in the acquired context
* @wctxt: The write context that will be handed to the write function
@@ -1048,6 +1061,8 @@ static bool nbcon_emit_next_record(struct nbcon_write_context *wctxt, bool use_a
/* Initialize the write context for driver callbacks. */
nbcon_write_context_set_buf(wctxt, &pmsg.pbufs->outbuf[0], pmsg.outbuf_len);
+ wctxt_load_execution_ctx(wctxt, &pmsg);
+
if (use_atomic)
con->write_atomic(con, wctxt);
else
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 1d765ad242b82..7daaa27705339 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2131,12 +2131,37 @@ static inline void printk_delay(int level)
}
}
+#define CALLER_ID_MASK 0x80000000
+
static inline u32 printk_caller_id(void)
{
return in_task() ? task_pid_nr(current) :
- 0x80000000 + smp_processor_id();
+ CALLER_ID_MASK + smp_processor_id();
+}
+
+#ifdef CONFIG_PRINTK_EXECUTION_CTX
+/* Store the opposite info than caller_id. */
+static u32 printk_caller_id2(void)
+{
+ return !in_task() ? task_pid_nr(current) :
+ CALLER_ID_MASK + smp_processor_id();
}
+static pid_t printk_info_get_pid(const struct printk_info *info)
+{
+ u32 caller_id = info->caller_id;
+ u32 caller_id2 = info->caller_id2;
+
+ return caller_id & CALLER_ID_MASK ? caller_id2 : caller_id;
+}
+
+static int printk_info_get_cpu(const struct printk_info *info)
+{
+ return ((info->caller_id & CALLER_ID_MASK ?
+ info->caller_id : info->caller_id2) & ~CALLER_ID_MASK);
+}
+#endif
+
/**
* printk_parse_prefix - Parse level and control flags.
*
@@ -2213,6 +2238,27 @@ static u16 printk_sprint(char *text, u16 size, int facility,
return text_len;
}
+#ifdef CONFIG_PRINTK_EXECUTION_CTX
+static void printk_store_execution_ctx(struct printk_info *info)
+{
+ info->caller_id2 = printk_caller_id2();
+ get_task_comm(info->comm, current);
+}
+
+static void pmsg_load_execution_ctx(struct printk_message *pmsg,
+ const struct printk_info *info)
+{
+ pmsg->cpu = printk_info_get_cpu(info);
+ pmsg->pid = printk_info_get_pid(info);
+ memcpy(pmsg->comm, info->comm, TASK_COMM_LEN);
+}
+#else
+static void printk_store_execution_ctx(struct printk_info *info) {}
+
+static void pmsg_load_execution_ctx(struct printk_message *pmsg,
+ const struct printk_info *info) {}
+#endif
+
__printf(4, 0)
int vprintk_store(int facility, int level,
const struct dev_printk_info *dev_info,
@@ -2320,6 +2366,7 @@ int vprintk_store(int facility, int level,
r.info->caller_id = caller_id;
if (dev_info)
memcpy(&r.info->dev_info, dev_info, sizeof(r.info->dev_info));
+ printk_store_execution_ctx(r.info);
/* A message without a trailing newline can be continued. */
if (!(flags & LOG_NEWLINE))
@@ -3002,6 +3049,7 @@ bool printk_get_next_message(struct printk_message *pmsg, u64 seq,
pmsg->seq = r.info->seq;
pmsg->dropped = r.info->seq - seq;
force_con = r.info->flags & LOG_FORCE_CON;
+ pmsg_load_execution_ctx(pmsg, r.info);
/*
* Skip records that are not forced to be printed on consoles and that
diff --git a/kernel/printk/printk_ringbuffer.h b/kernel/printk/printk_ringbuffer.h
index 4ef81349d9fbe..1651b53ece34f 100644
--- a/kernel/printk/printk_ringbuffer.h
+++ b/kernel/printk/printk_ringbuffer.h
@@ -23,6 +23,11 @@ struct printk_info {
u8 flags:5; /* internal record flags */
u8 level:3; /* syslog level */
u32 caller_id; /* thread id or processor id */
+#ifdef CONFIG_PRINTK_EXECUTION_CTX
+ u32 caller_id2; /* caller_id complement */
+ /* name of the task that generated the message */
+ char comm[TASK_COMM_LEN];
+#endif
struct dev_printk_info dev_info;
};
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index ba36939fda79b..57f91ee10b8e6 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -35,6 +35,26 @@ config PRINTK_CALLER
no option to enable/disable at the kernel command line parameter or
sysfs interface.
+config CONSOLE_HAS_EXECUTION_CTX
+ bool
+ help
+ Selected by console drivers that support execution context
+ (task name/CPU) in their output. This enables PRINTK_EXECUTION_CTX
+ to provide the necessary infrastructure.
+
+config PRINTK_EXECUTION_CTX
+ bool "Include execution context (task/CPU) in printk messages"
+ depends on PRINTK && CONSOLE_HAS_EXECUTION_CTX
+ default CONSOLE_HAS_EXECUTION_CTX
+ help
+ This option extends struct printk_info to include extra execution
+ context in printk, such as task name and CPU number from where the
+ message originated. This is useful for correlating printk messages
+ with specific execution contexts.
+
+ This is automatically enabled when a console driver that supports
+ execution context is selected.
+
config STACKTRACE_BUILD_ID
bool "Show build ID information in stacktraces"
depends on PRINTK
--
2.47.3
^ permalink raw reply related [flat|nested] 9+ messages in thread* Re: [PATCH net-next v4 1/5] printk: Add execution context (task name/CPU) to printk_info
2026-01-23 12:17 ` [PATCH net-next v4 1/5] printk: Add execution context (task name/CPU) to printk_info Breno Leitao
@ 2026-01-27 14:58 ` Paolo Abeni
2026-01-27 20:43 ` John Ogness
1 sibling, 0 replies; 9+ messages in thread
From: Paolo Abeni @ 2026-01-27 14:58 UTC (permalink / raw)
To: Breno Leitao, Andrew Lunn, David S. Miller, Eric Dumazet,
Jakub Kicinski, pmladek, john.ogness
Cc: Greg Kroah-Hartman, Steven Rostedt, Sergey Senozhatsky,
Andrew Morton, netdev, linux-kernel, asantostc, efault, gustavold,
calvin, jv, mpdesouza, kernel-team
On 1/23/26 1:17 PM, Breno Leitao wrote:
> Extend struct printk_info to include the task name, pid, and CPU
> number where printk messages originate. This information is captured
> at vprintk_store() time and propagated through printk_message to
> nbcon_write_context, making it available to nbcon console drivers.
>
> This is useful for consoles like netconsole that want to include
> execution context in their output, allowing correlation of messages
> with specific tasks and CPUs regardless of where the console driver
> actually runs.
>
> The feature is controlled by CONFIG_PRINTK_EXECUTION_CTX, which is
> automatically selected by CONFIG_NETCONSOLE_DYNAMIC. When disabled,
> the helper functions compile to no-ops with no overhead.
>
> Suggested-by: John Ogness <john.ogness@linutronix.de>
> Signed-off-by: Breno Leitao <leitao@debian.org>
> Signed-off-by: Petr Mladek <pmladek@suse.com>
The netconsole bits in later patches LGTM, but we need explicit ack from
printk maintainers here.
Thanks,
Paolo
^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH net-next v4 1/5] printk: Add execution context (task name/CPU) to printk_info
2026-01-23 12:17 ` [PATCH net-next v4 1/5] printk: Add execution context (task name/CPU) to printk_info Breno Leitao
2026-01-27 14:58 ` Paolo Abeni
@ 2026-01-27 20:43 ` John Ogness
2026-01-28 10:52 ` Breno Leitao
1 sibling, 1 reply; 9+ messages in thread
From: John Ogness @ 2026-01-27 20:43 UTC (permalink / raw)
To: Breno Leitao, Breno Leitao, Andrew Lunn, David S. Miller,
Eric Dumazet, Jakub Kicinski, Paolo Abeni, pmladek
Cc: Greg Kroah-Hartman, Steven Rostedt, Sergey Senozhatsky,
Andrew Morton, netdev, linux-kernel, asantostc, efault, gustavold,
calvin, jv, mpdesouza, kernel-team
On 2026-01-23, Breno Leitao <leitao@debian.org> wrote:
> diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c
> index 32fc12e536752..391a58be0c5b3 100644
> --- a/kernel/printk/nbcon.c
> +++ b/kernel/printk/nbcon.c
> @@ -946,6 +946,19 @@ void nbcon_reacquire_nobuf(struct nbcon_write_context *wctxt)
> }
> EXPORT_SYMBOL_GPL(nbcon_reacquire_nobuf);
>
> +#ifdef CONFIG_PRINTK_EXECUTION_CTX
> +static void wctxt_load_execution_ctx(struct nbcon_write_context *wctxt,
> + struct printk_message *pmsg)
> +{
> + wctxt->cpu = pmsg->cpu;
> + wctxt->pid = pmsg->pid;
> + memcpy(wctxt->comm, pmsg->comm, TASK_COMM_LEN);
Perhaps using sizeof() instead?
memcpy(wctxt->comm, pmsg->comm, sizeof(wctxt->comm));
And adding a static assert that the sizes match?
static_assert(sizeof(wctxt->comm) == sizeof(pmsg->comm));
> +}
[...]
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index 1d765ad242b82..7daaa27705339 100644
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -2131,12 +2131,37 @@ static inline void printk_delay(int level)
> }
> }
>
> +#define CALLER_ID_MASK 0x80000000
> +
> static inline u32 printk_caller_id(void)
> {
> return in_task() ? task_pid_nr(current) :
> - 0x80000000 + smp_processor_id();
> + CALLER_ID_MASK + smp_processor_id();
> +}
> +
> +#ifdef CONFIG_PRINTK_EXECUTION_CTX
> +/* Store the opposite info than caller_id. */
> +static u32 printk_caller_id2(void)
> +{
> + return !in_task() ? task_pid_nr(current) :
> + CALLER_ID_MASK + smp_processor_id();
> }
>
> +static pid_t printk_info_get_pid(const struct printk_info *info)
> +{
> + u32 caller_id = info->caller_id;
> + u32 caller_id2 = info->caller_id2;
> +
> + return caller_id & CALLER_ID_MASK ? caller_id2 : caller_id;
> +}
> +
> +static int printk_info_get_cpu(const struct printk_info *info)
> +{
> + return ((info->caller_id & CALLER_ID_MASK ?
> + info->caller_id : info->caller_id2) & ~CALLER_ID_MASK);
> +}
It is a bit odd that printk_info_get_pid() uses local variables and
printk_info_get_cpu() does not. I could understand if things evolve that
way over time, but it is odd to use the two different styles from the
beginning.
I would prefer the local variable variant. But mostly I would prefer
that they are the same style.
> +#endif
> +
> /**
> * printk_parse_prefix - Parse level and control flags.
> *
> @@ -2213,6 +2238,27 @@ static u16 printk_sprint(char *text, u16 size, int facility,
> return text_len;
> }
>
> +#ifdef CONFIG_PRINTK_EXECUTION_CTX
> +static void printk_store_execution_ctx(struct printk_info *info)
> +{
> + info->caller_id2 = printk_caller_id2();
> + get_task_comm(info->comm, current);
> +}
> +
> +static void pmsg_load_execution_ctx(struct printk_message *pmsg,
> + const struct printk_info *info)
> +{
> + pmsg->cpu = printk_info_get_cpu(info);
> + pmsg->pid = printk_info_get_pid(info);
> + memcpy(pmsg->comm, info->comm, TASK_COMM_LEN);
Here I also suggest using sizeof() and static_assert():
memcpy(pmsg->comm, info->comm, sizeof(pmsg->comm));
static_assert(sizeof(pmsg->comm) == sizeof(info->comm));
John Ogness
^ permalink raw reply [flat|nested] 9+ messages in thread* Re: [PATCH net-next v4 1/5] printk: Add execution context (task name/CPU) to printk_info
2026-01-27 20:43 ` John Ogness
@ 2026-01-28 10:52 ` Breno Leitao
0 siblings, 0 replies; 9+ messages in thread
From: Breno Leitao @ 2026-01-28 10:52 UTC (permalink / raw)
To: John Ogness
Cc: Andrew Lunn, David S. Miller, Eric Dumazet, Jakub Kicinski,
Paolo Abeni, pmladek, Greg Kroah-Hartman, Steven Rostedt,
Sergey Senozhatsky, Andrew Morton, netdev, linux-kernel,
asantostc, efault, gustavold, calvin, jv, mpdesouza, kernel-team
Hello John,
On Tue, Jan 27, 2026 at 09:49:25PM +0106, John Ogness wrote:
> On 2026-01-23, Breno Leitao <leitao@debian.org> wrote:
> > diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c
> > index 32fc12e536752..391a58be0c5b3 100644
> > --- a/kernel/printk/nbcon.c
> > +++ b/kernel/printk/nbcon.c
> > @@ -946,6 +946,19 @@ void nbcon_reacquire_nobuf(struct nbcon_write_context *wctxt)
> > }
> > EXPORT_SYMBOL_GPL(nbcon_reacquire_nobuf);
> >
> > +#ifdef CONFIG_PRINTK_EXECUTION_CTX
> > +static void wctxt_load_execution_ctx(struct nbcon_write_context *wctxt,
> > + struct printk_message *pmsg)
> > +{
> > + wctxt->cpu = pmsg->cpu;
> > + wctxt->pid = pmsg->pid;
> > + memcpy(wctxt->comm, pmsg->comm, TASK_COMM_LEN);
>
> Perhaps using sizeof() instead?
>
> memcpy(wctxt->comm, pmsg->comm, sizeof(wctxt->comm));
>
> And adding a static assert that the sizes match?
>
> static_assert(sizeof(wctxt->comm) == sizeof(pmsg->comm));
Sure, I move the size from TASK_COMM_LEN to sizeof(wctxt->comm) and also
adding the build time assert.
> > diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> > index 1d765ad242b82..7daaa27705339 100644
> > --- a/kernel/printk/printk.c
> > +++ b/kernel/printk/printk.c
> > @@ -2131,12 +2131,37 @@ static inline void printk_delay(int level)
> > }
> > }
> >
> > +#define CALLER_ID_MASK 0x80000000
> > +
> > static inline u32 printk_caller_id(void)
> > {
> > return in_task() ? task_pid_nr(current) :
> > - 0x80000000 + smp_processor_id();
> > + CALLER_ID_MASK + smp_processor_id();
> > +}
> > +
> > +#ifdef CONFIG_PRINTK_EXECUTION_CTX
> > +/* Store the opposite info than caller_id. */
> > +static u32 printk_caller_id2(void)
> > +{
> > + return !in_task() ? task_pid_nr(current) :
> > + CALLER_ID_MASK + smp_processor_id();
> > }
> >
> > +static pid_t printk_info_get_pid(const struct printk_info *info)
> > +{
> > + u32 caller_id = info->caller_id;
> > + u32 caller_id2 = info->caller_id2;
> > +
> > + return caller_id & CALLER_ID_MASK ? caller_id2 : caller_id;
> > +}
> > +
> > +static int printk_info_get_cpu(const struct printk_info *info)
> > +{
> > + return ((info->caller_id & CALLER_ID_MASK ?
> > + info->caller_id : info->caller_id2) & ~CALLER_ID_MASK);
> > +}
>
> It is a bit odd that printk_info_get_pid() uses local variables and
> printk_info_get_cpu() does not. I could understand if things evolve that
> way over time, but it is odd to use the two different styles from the
> beginning.
>
> I would prefer the local variable variant. But mostly I would prefer
> that they are the same style.
They evolve different, I will get both of them using local variables and
in the same style.
> > +
> > +static void pmsg_load_execution_ctx(struct printk_message *pmsg,
> > + const struct printk_info *info)
> > +{
> > + pmsg->cpu = printk_info_get_cpu(info);
> > + pmsg->pid = printk_info_get_pid(info);
> > + memcpy(pmsg->comm, info->comm, TASK_COMM_LEN);
>
> Here I also suggest using sizeof() and static_assert():
>
> memcpy(pmsg->comm, info->comm, sizeof(pmsg->comm));
> static_assert(sizeof(pmsg->comm) == sizeof(info->comm));
Ack! I will respin it.
Thanks for the review,
--breno
^ permalink raw reply [flat|nested] 9+ messages in thread
* [PATCH net-next v4 2/5] netconsole: extract message fragmentation into send_msg_udp()
2026-01-23 12:17 [PATCH net-next v4 0/5] net: netconsole: convert to NBCON console infrastructure Breno Leitao
2026-01-23 12:17 ` [PATCH net-next v4 1/5] printk: Add execution context (task name/CPU) to printk_info Breno Leitao
@ 2026-01-23 12:17 ` Breno Leitao
2026-01-23 12:17 ` [PATCH net-next v4 3/5] netconsole: convert to NBCON console infrastructure Breno Leitao
` (2 subsequent siblings)
4 siblings, 0 replies; 9+ messages in thread
From: Breno Leitao @ 2026-01-23 12:17 UTC (permalink / raw)
To: Breno Leitao, Andrew Lunn, David S. Miller, Eric Dumazet,
Jakub Kicinski, Paolo Abeni, pmladek, john.ogness
Cc: Greg Kroah-Hartman, Steven Rostedt, Sergey Senozhatsky,
Andrew Morton, netdev, linux-kernel, asantostc, efault, gustavold,
calvin, jv, mpdesouza, kernel-team, Simon Horman
Extract the message fragmentation logic from write_msg() into a
dedicated send_msg_udp() function. This improves code readability
and prepares for future enhancements.
The new send_msg_udp() function handles splitting messages that
exceed MAX_PRINT_CHUNK into smaller fragments and sending them
sequentially. This function is placed before send_ext_msg_udp()
to maintain a logical ordering of related functions.
No functional changes - this is purely a refactoring commit.
Reviewed-by: Petr Mladek <pmladek@suse.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Breno Leitao <leitao@debian.org>
---
drivers/net/netconsole.c | 24 +++++++++++++++---------
1 file changed, 15 insertions(+), 9 deletions(-)
diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index 82c232f9ede24..e37250bf495fa 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -1876,12 +1876,24 @@ static void write_ext_msg(struct console *con, const char *msg,
spin_unlock_irqrestore(&target_list_lock, flags);
}
+static void send_msg_udp(struct netconsole_target *nt, const char *msg,
+ unsigned int len)
+{
+ const char *tmp = msg;
+ int frag, left = len;
+
+ while (left > 0) {
+ frag = min(left, MAX_PRINT_CHUNK);
+ send_udp(nt, tmp, frag);
+ tmp += frag;
+ left -= frag;
+ }
+}
+
static void write_msg(struct console *con, const char *msg, unsigned int len)
{
- int frag, left;
unsigned long flags;
struct netconsole_target *nt;
- const char *tmp;
if (oops_only && !oops_in_progress)
return;
@@ -1899,13 +1911,7 @@ static void write_msg(struct console *con, const char *msg, unsigned int len)
* at least one target if we die inside here, instead
* of unnecessarily keeping all targets in lock-step.
*/
- tmp = msg;
- for (left = len; left;) {
- frag = min(left, MAX_PRINT_CHUNK);
- send_udp(nt, tmp, frag);
- tmp += frag;
- left -= frag;
- }
+ send_msg_udp(nt, msg, len);
}
}
spin_unlock_irqrestore(&target_list_lock, flags);
--
2.47.3
^ permalink raw reply related [flat|nested] 9+ messages in thread* [PATCH net-next v4 3/5] netconsole: convert to NBCON console infrastructure
2026-01-23 12:17 [PATCH net-next v4 0/5] net: netconsole: convert to NBCON console infrastructure Breno Leitao
2026-01-23 12:17 ` [PATCH net-next v4 1/5] printk: Add execution context (task name/CPU) to printk_info Breno Leitao
2026-01-23 12:17 ` [PATCH net-next v4 2/5] netconsole: extract message fragmentation into send_msg_udp() Breno Leitao
@ 2026-01-23 12:17 ` Breno Leitao
2026-01-23 12:17 ` [PATCH net-next v4 4/5] netconsole: Use printk context for CPU and task information Breno Leitao
2026-01-23 12:17 ` [PATCH net-next v4 5/5] netconsole: pass wctxt to send_msg_udp() for consistency Breno Leitao
4 siblings, 0 replies; 9+ messages in thread
From: Breno Leitao @ 2026-01-23 12:17 UTC (permalink / raw)
To: Breno Leitao, Andrew Lunn, David S. Miller, Eric Dumazet,
Jakub Kicinski, Paolo Abeni, pmladek, john.ogness
Cc: Greg Kroah-Hartman, Steven Rostedt, Sergey Senozhatsky,
Andrew Morton, netdev, linux-kernel, asantostc, efault, gustavold,
calvin, jv, mpdesouza, kernel-team
Convert netconsole from the legacy console API to the NBCON framework.
NBCON provides threaded printing which unblocks printk()s and flushes in
a thread, decoupling network TX from printk() when netconsole is
in use.
Since netconsole relies on the network stack which cannot safely operate
from all atomic contexts, mark both consoles with
CON_NBCON_ATOMIC_UNSAFE. (See discussion in [1])
CON_NBCON_ATOMIC_UNSAFE restricts write_atomic() usage to emergency
scenarios (panic) where regular messages are sent in threaded mode.
Implementation changes:
- Unify write_ext_msg() and write_msg() into netconsole_write()
- Add device_lock/device_unlock callbacks to manage target_list_lock
- Use nbcon_enter_unsafe()/nbcon_exit_unsafe() around network
operations.
- If nbcon_enter_unsafe() fails, just return given netconsole lost
the ownership of the console.
- Set write_thread and write_atomic callbacks (both use same function)
Link: https://lore.kernel.org/all/b2qps3uywhmjaym4mht2wpxul4yqtuuayeoq4iv4k3zf5wdgh3@tocu6c7mj4lt/ [1]
Signed-off-by: Breno Leitao <leitao@debian.org>
---
drivers/net/netconsole.c | 101 +++++++++++++++++++++++++++++------------------
1 file changed, 62 insertions(+), 39 deletions(-)
diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index e37250bf495fa..ec000f477c2a8 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -1859,23 +1859,6 @@ static void send_ext_msg_udp(struct netconsole_target *nt, const char *msg,
sysdata_len);
}
-static void write_ext_msg(struct console *con, const char *msg,
- unsigned int len)
-{
- struct netconsole_target *nt;
- unsigned long flags;
-
- if ((oops_only && !oops_in_progress) || list_empty(&target_list))
- return;
-
- spin_lock_irqsave(&target_list_lock, flags);
- list_for_each_entry(nt, &target_list, list)
- if (nt->extended && nt->state == STATE_ENABLED &&
- netif_running(nt->np.dev))
- send_ext_msg_udp(nt, msg, len);
- spin_unlock_irqrestore(&target_list_lock, flags);
-}
-
static void send_msg_udp(struct netconsole_target *nt, const char *msg,
unsigned int len)
{
@@ -1890,30 +1873,64 @@ static void send_msg_udp(struct netconsole_target *nt, const char *msg,
}
}
-static void write_msg(struct console *con, const char *msg, unsigned int len)
+/**
+ * netconsole_write - Generic function to send a msg to all targets
+ * @wctxt: nbcon write context
+ * @extended: "true" for extended console mode
+ *
+ * Given an nbcon write context, send the message to the netconsole targets
+ */
+static void netconsole_write(struct nbcon_write_context *wctxt, bool extended)
{
- unsigned long flags;
struct netconsole_target *nt;
if (oops_only && !oops_in_progress)
return;
- /* Avoid taking lock and disabling interrupts unnecessarily */
- if (list_empty(&target_list))
- return;
- spin_lock_irqsave(&target_list_lock, flags);
list_for_each_entry(nt, &target_list, list) {
- if (!nt->extended && nt->state == STATE_ENABLED &&
- netif_running(nt->np.dev)) {
- /*
- * We nest this inside the for-each-target loop above
- * so that we're able to get as much logging out to
- * at least one target if we die inside here, instead
- * of unnecessarily keeping all targets in lock-step.
- */
- send_msg_udp(nt, msg, len);
- }
+ if (nt->extended != extended || nt->state != STATE_ENABLED ||
+ !netif_running(nt->np.dev))
+ continue;
+
+ /* If nbcon_enter_unsafe() fails, just return given netconsole
+ * lost the ownership, and iterating over the targets will not
+ * be able to re-acquire.
+ */
+ if (!nbcon_enter_unsafe(wctxt))
+ return;
+
+ if (extended)
+ send_ext_msg_udp(nt, wctxt->outbuf, wctxt->len);
+ else
+ send_msg_udp(nt, wctxt->outbuf, wctxt->len);
+
+ nbcon_exit_unsafe(wctxt);
}
+}
+
+static void netconsole_write_ext(struct console *con __always_unused,
+ struct nbcon_write_context *wctxt)
+{
+ netconsole_write(wctxt, true);
+}
+
+static void netconsole_write_basic(struct console *con __always_unused,
+ struct nbcon_write_context *wctxt)
+{
+ netconsole_write(wctxt, false);
+}
+
+static void netconsole_device_lock(struct console *con __always_unused,
+ unsigned long *flags)
+__acquires(&target_list_lock)
+{
+ spin_lock_irqsave(&target_list_lock, *flags);
+}
+
+static void netconsole_device_unlock(struct console *con __always_unused,
+ unsigned long flags)
+__releases(&target_list_lock)
+{
spin_unlock_irqrestore(&target_list_lock, flags);
}
@@ -2077,15 +2094,21 @@ static void free_param_target(struct netconsole_target *nt)
}
static struct console netconsole_ext = {
- .name = "netcon_ext",
- .flags = CON_ENABLED | CON_EXTENDED,
- .write = write_ext_msg,
+ .name = "netcon_ext",
+ .flags = CON_ENABLED | CON_EXTENDED | CON_NBCON | CON_NBCON_ATOMIC_UNSAFE,
+ .write_thread = netconsole_write_ext,
+ .write_atomic = netconsole_write_ext,
+ .device_lock = netconsole_device_lock,
+ .device_unlock = netconsole_device_unlock,
};
static struct console netconsole = {
- .name = "netcon",
- .flags = CON_ENABLED,
- .write = write_msg,
+ .name = "netcon",
+ .flags = CON_ENABLED | CON_NBCON | CON_NBCON_ATOMIC_UNSAFE,
+ .write_thread = netconsole_write_basic,
+ .write_atomic = netconsole_write_basic,
+ .device_lock = netconsole_device_lock,
+ .device_unlock = netconsole_device_unlock,
};
static int __init init_netconsole(void)
--
2.47.3
^ permalink raw reply related [flat|nested] 9+ messages in thread* [PATCH net-next v4 4/5] netconsole: Use printk context for CPU and task information
2026-01-23 12:17 [PATCH net-next v4 0/5] net: netconsole: convert to NBCON console infrastructure Breno Leitao
` (2 preceding siblings ...)
2026-01-23 12:17 ` [PATCH net-next v4 3/5] netconsole: convert to NBCON console infrastructure Breno Leitao
@ 2026-01-23 12:17 ` Breno Leitao
2026-01-23 12:17 ` [PATCH net-next v4 5/5] netconsole: pass wctxt to send_msg_udp() for consistency Breno Leitao
4 siblings, 0 replies; 9+ messages in thread
From: Breno Leitao @ 2026-01-23 12:17 UTC (permalink / raw)
To: Breno Leitao, Andrew Lunn, David S. Miller, Eric Dumazet,
Jakub Kicinski, Paolo Abeni, pmladek, john.ogness
Cc: Greg Kroah-Hartman, Steven Rostedt, Sergey Senozhatsky,
Andrew Morton, netdev, linux-kernel, asantostc, efault, gustavold,
calvin, jv, mpdesouza, kernel-team
Use the CPU and task name captured at printk() time from
nbcon_write_context instead of querying the current execution context.
This provides accurate information about where the message originated,
rather than where netconsole happens to be running.
For CPU, use wctxt->msg_cpu instead of raw_smp_processor_id().
For taskname, use wctxt->msg_comm directly which contains the task
name captured at printk time.
This change ensures netconsole outputs reflect the actual context that
generated the log message, which is especially important when the
console driver runs asynchronously in a dedicated thread.
Signed-off-by: Breno Leitao <leitao@debian.org>
---
drivers/net/netconsole.c | 40 +++++++++++++++++++++++-----------------
1 file changed, 23 insertions(+), 17 deletions(-)
diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index ec000f477c2a8..0f44ce5ccc0ab 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -1490,18 +1490,20 @@ static void populate_configfs_item(struct netconsole_target *nt,
init_target_config_group(nt, target_name);
}
-static int sysdata_append_cpu_nr(struct netconsole_target *nt, int offset)
+static int sysdata_append_cpu_nr(struct netconsole_target *nt, int offset,
+ struct nbcon_write_context *wctxt)
{
return scnprintf(&nt->sysdata[offset],
MAX_EXTRADATA_ENTRY_LEN, " cpu=%u\n",
- raw_smp_processor_id());
+ wctxt->cpu);
}
-static int sysdata_append_taskname(struct netconsole_target *nt, int offset)
+static int sysdata_append_taskname(struct netconsole_target *nt, int offset,
+ struct nbcon_write_context *wctxt)
{
return scnprintf(&nt->sysdata[offset],
MAX_EXTRADATA_ENTRY_LEN, " taskname=%s\n",
- current->comm);
+ wctxt->comm);
}
static int sysdata_append_release(struct netconsole_target *nt, int offset)
@@ -1522,8 +1524,10 @@ static int sysdata_append_msgid(struct netconsole_target *nt, int offset)
/*
* prepare_sysdata - append sysdata in runtime
* @nt: target to send message to
+ * @wctxt: nbcon write context containing message metadata
*/
-static int prepare_sysdata(struct netconsole_target *nt)
+static int prepare_sysdata(struct netconsole_target *nt,
+ struct nbcon_write_context *wctxt)
{
int sysdata_len = 0;
@@ -1531,9 +1535,9 @@ static int prepare_sysdata(struct netconsole_target *nt)
goto out;
if (nt->sysdata_fields & SYSDATA_CPU_NR)
- sysdata_len += sysdata_append_cpu_nr(nt, sysdata_len);
+ sysdata_len += sysdata_append_cpu_nr(nt, sysdata_len, wctxt);
if (nt->sysdata_fields & SYSDATA_TASKNAME)
- sysdata_len += sysdata_append_taskname(nt, sysdata_len);
+ sysdata_len += sysdata_append_taskname(nt, sysdata_len, wctxt);
if (nt->sysdata_fields & SYSDATA_RELEASE)
sysdata_len += sysdata_append_release(nt, sysdata_len);
if (nt->sysdata_fields & SYSDATA_MSGID)
@@ -1831,31 +1835,33 @@ static void send_msg_fragmented(struct netconsole_target *nt,
/**
* send_ext_msg_udp - send extended log message to target
* @nt: target to send message to
- * @msg: extended log message to send
- * @msg_len: length of message
+ * @wctxt: nbcon write context containing message and metadata
*
- * Transfer extended log @msg to @nt. If @msg is longer than
+ * Transfer extended log message to @nt. If message is longer than
* MAX_PRINT_CHUNK, it'll be split and transmitted in multiple chunks with
* ncfrag header field added to identify them.
*/
-static void send_ext_msg_udp(struct netconsole_target *nt, const char *msg,
- int msg_len)
+static void send_ext_msg_udp(struct netconsole_target *nt,
+ struct nbcon_write_context *wctxt)
{
int userdata_len = 0;
int release_len = 0;
int sysdata_len = 0;
+ int len;
#ifdef CONFIG_NETCONSOLE_DYNAMIC
- sysdata_len = prepare_sysdata(nt);
+ sysdata_len = prepare_sysdata(nt, wctxt);
userdata_len = nt->userdata_length;
#endif
if (nt->release)
release_len = strlen(init_utsname()->release) + 1;
- if (msg_len + release_len + sysdata_len + userdata_len <= MAX_PRINT_CHUNK)
- return send_msg_no_fragmentation(nt, msg, msg_len, release_len);
+ len = wctxt->len + release_len + sysdata_len + userdata_len;
+ if (len <= MAX_PRINT_CHUNK)
+ return send_msg_no_fragmentation(nt, wctxt->outbuf,
+ wctxt->len, release_len);
- return send_msg_fragmented(nt, msg, msg_len, release_len,
+ return send_msg_fragmented(nt, wctxt->outbuf, wctxt->len, release_len,
sysdata_len);
}
@@ -1900,7 +1906,7 @@ static void netconsole_write(struct nbcon_write_context *wctxt, bool extended)
return;
if (extended)
- send_ext_msg_udp(nt, wctxt->outbuf, wctxt->len);
+ send_ext_msg_udp(nt, wctxt);
else
send_msg_udp(nt, wctxt->outbuf, wctxt->len);
--
2.47.3
^ permalink raw reply related [flat|nested] 9+ messages in thread* [PATCH net-next v4 5/5] netconsole: pass wctxt to send_msg_udp() for consistency
2026-01-23 12:17 [PATCH net-next v4 0/5] net: netconsole: convert to NBCON console infrastructure Breno Leitao
` (3 preceding siblings ...)
2026-01-23 12:17 ` [PATCH net-next v4 4/5] netconsole: Use printk context for CPU and task information Breno Leitao
@ 2026-01-23 12:17 ` Breno Leitao
4 siblings, 0 replies; 9+ messages in thread
From: Breno Leitao @ 2026-01-23 12:17 UTC (permalink / raw)
To: Breno Leitao, Andrew Lunn, David S. Miller, Eric Dumazet,
Jakub Kicinski, Paolo Abeni, pmladek, john.ogness
Cc: Greg Kroah-Hartman, Steven Rostedt, Sergey Senozhatsky,
Andrew Morton, netdev, linux-kernel, asantostc, efault, gustavold,
calvin, jv, mpdesouza, kernel-team
Refactor send_msg_udp() to take a struct nbcon_write_context pointer
instead of separate msg and len parameters. This makes its signature
consistent with send_ext_msg_udp() and prepares the function for
future use of execution context information from wctxt.
No functional change.
Signed-off-by: Breno Leitao <leitao@debian.org>
---
drivers/net/netconsole.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)
diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index 0f44ce5ccc0ab..d1dadb7e0350f 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -1865,16 +1865,16 @@ static void send_ext_msg_udp(struct netconsole_target *nt,
sysdata_len);
}
-static void send_msg_udp(struct netconsole_target *nt, const char *msg,
- unsigned int len)
+static void send_msg_udp(struct netconsole_target *nt,
+ struct nbcon_write_context *wctxt)
{
- const char *tmp = msg;
- int frag, left = len;
+ const char *msg = wctxt->outbuf;
+ int frag, left = wctxt->len;
while (left > 0) {
frag = min(left, MAX_PRINT_CHUNK);
- send_udp(nt, tmp, frag);
- tmp += frag;
+ send_udp(nt, msg, frag);
+ msg += frag;
left -= frag;
}
}
@@ -1908,7 +1908,7 @@ static void netconsole_write(struct nbcon_write_context *wctxt, bool extended)
if (extended)
send_ext_msg_udp(nt, wctxt);
else
- send_msg_udp(nt, wctxt->outbuf, wctxt->len);
+ send_msg_udp(nt, wctxt);
nbcon_exit_unsafe(wctxt);
}
--
2.47.3
^ permalink raw reply related [flat|nested] 9+ messages in thread