From nobody Sun Feb 8 20:52:09 2026 Received: from stravinsky.debian.org (stravinsky.debian.org [82.195.75.108]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1C0C63033D8; Tue, 3 Feb 2026 17:24:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=82.195.75.108 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770139474; cv=none; b=VRt72vmup9qzKGmSTk1bE9jjjXLGlwGui1o6pM/eJPvg3a/Y/N71jMQtMQ95/FUUPb1J5qjdopgcOiRA6xZmWCoLO96c6bhnu0sgARNJ/YaZooUIvE92qVGt6LblqoRzuL++cUMhdFq6W2heiDww+QqLPIXGJic7t4DCKXxq9k4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770139474; c=relaxed/simple; bh=YW6T6corvYXvJqvQzvitkQL9TeapEvUtc5oj+Na3RSM=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=TdCHDEMIV0X1EAxj0zSEmsw99Usu4F/sOG01wcWm9zhNgw0vacT6WpAqXHFwamfnvyeFyokdfLz6Y3SRbeFxU+a8dH55WbJAmjoN11melEGjTEEO1Q8hh/wfXyWbK+ZKWEeyt+PHOy/4a1FI6tfkpZrRMjmKjsm2Z26ho/aKy4c= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=debian.org; spf=none smtp.mailfrom=debian.org; dkim=pass (2048-bit key) header.d=debian.org header.i=@debian.org header.b=sUpKgjq/; arc=none smtp.client-ip=82.195.75.108 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=debian.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=debian.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=debian.org header.i=@debian.org header.b="sUpKgjq/" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=debian.org; s=smtpauto.stravinsky; h=X-Debian-User:Cc:To:In-Reply-To:References: Message-Id:Content-Transfer-Encoding:Content-Type:MIME-Version:Subject:Date: From:Reply-To:Content-ID:Content-Description; bh=pSKJ1yzY2SZrxK97G6vs4bf2Lq4Zd0Es8GeF/sYwarA=; b=sUpKgjq//r9Gf7s7gaknDGxSPk rlpafCZvCaek5Ky2nxYYVP4fxFFC0OzQDK/jblOr6P2rgKt3fZsBYO5WLSOLYzDH+GWma3CLS09Eb DB/KnFmf0xcOuso7+vJYutMH8du8VsciAUUprRTt6t6DwDetWPe3ai6DzqmEG2woguuhYbMOYosS9 xEtmYFGRX2Kd3fT7rtVbnjKxECDimJ1qAexPBCkaP1H0tKGiGl3lO8Naa85R0UEsi7HlBZcZlxioS JRHjcUIZfDO8u4s+SOGVemw5qdZ057txIDdRGhYTtqStEnNM1nf+CnEZf3MRCid165MWePczij5xF ckDmH61w==; Received: from authenticated user by stravinsky.debian.org with esmtpsa (TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim 4.94.2) (envelope-from ) id 1vnK8b-004z5K-Lz; Tue, 03 Feb 2026 17:24:30 +0000 From: Breno Leitao Date: Tue, 03 Feb 2026 09:23:52 -0800 Subject: [PATCH net-next v6 1/4] printk: Add execution context (task name/CPU) to printk_info Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20260203-nbcon-v6-1-985f3bdb3267@debian.org> References: <20260203-nbcon-v6-0-985f3bdb3267@debian.org> In-Reply-To: <20260203-nbcon-v6-0-985f3bdb3267@debian.org> To: Breno Leitao , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , pmladek@suse.com, john.ogness@linutronix.de Cc: Greg Kroah-Hartman , Steven Rostedt , Sergey Senozhatsky , Andrew Morton , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, asantostc@gmail.com, efault@gmx.de, gustavold@gmail.com, calvin@wbinvd.org, jv@jvosburgh.net, mpdesouza@suse.com, kernel-team@meta.com X-Mailer: b4 0.15-dev-f4305 X-Developer-Signature: v=1; a=openpgp-sha256; l=9303; i=leitao@debian.org; h=from:subject:message-id; bh=YW6T6corvYXvJqvQzvitkQL9TeapEvUtc5oj+Na3RSM=; b=owEBbQKS/ZANAwAIATWjk5/8eHdtAcsmYgBpgi9CwrgWmI9d3eZ/H8D5M+9wn5slujvfBb3H7 Is7PTPc5FqJAjMEAAEIAB0WIQSshTmm6PRnAspKQ5s1o5Of/Hh3bQUCaYIvQgAKCRA1o5Of/Hh3 bTmBD/94iveYF3y7pbFIj2sEnyVKo/wHnjNU+pkDyoAd73ami9Mx/Y6ULUIHJIG/LXDHX+XhSGb mKm3JJIG/dy6PWEfalDdaDIx70mfxQ+Wu3JJHNljpSLkICUhFE2+GaO3dgzgyzN4ub13xrkEiAx qR4r+HaBLsiqaD5Hnn+pkp821mKdJBsPv5rghqgCF+sgvsVPZ24twPndcpV7zROGDZnLu8wm0Fp lVwAsebF3mqW5oyOho5vEPmWDL4XAV2hTlymgwG3ymmMk1VoCbIS9wsGUng9ArYcDkE8PF3r9T4 9ql8XJFpFQNGbH/FY0aZxsbPNAutrhIJqeSimZuoS6FHnWFYAz9wxfWP/oKHNeaJWcNbCAeefbK w9H6jK0YeOqqitJda5GbCy9b1ueyVUgawd7relGCoD5P8BJM9GRWbfktsTbeLEbYwFB1wZB+UqK xPGmyx02MHlLIakzVlbWR//yordQLUuL2kFvcicEokx03gBUT0u4W4y5ovRzWuEz1HNnBim6A0m 2vKPAUD5mBVwS55WyVcNq4vYZmiFum7WEz0dYUYJ+PXkkCfeVnkwyh2zjOZ4rHy+smLAMwotf+i 5ad2ZYbs1jDFb1E5anWZ1C5LLE488dl/22oVWcZfDxs4k3LUO1ZcyjssJgNSCXBl/Rs8jpY+mOi lga4KLF8bdVudrw== X-Developer-Key: i=leitao@debian.org; a=openpgp; fpr=AC8539A6E8F46702CA4A439B35A3939FFC78776D X-Debian-User: leitao 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 Signed-off-by: Breno Leitao Signed-off-by: Petr Mladek Reviewed-by: Petr Mladek --- drivers/net/Kconfig | 1 + include/linux/console.h | 8 ++++++ kernel/printk/internal.h | 8 ++++++ kernel/printk/nbcon.c | 16 ++++++++++++ kernel/printk/printk.c | 54 +++++++++++++++++++++++++++++++++++= +++- kernel/printk/printk_ringbuffer.h | 5 ++++ lib/Kconfig.debug | 20 +++++++++++++++ 7 files changed, 111 insertions(+), 1 deletion(-) diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig index 9c7953f8e6377..2af4d2ef5437c 100644 --- a/drivers/net/Kconfig +++ b/drivers/net/Kconfig @@ -341,6 +341,7 @@ config NETCONSOLE_DYNAMIC bool "Dynamic reconfiguration of logging targets" depends on NETCONSOLE && SYSFS && CONFIGFS_FS && \ !(NETCONSOLE=3Dy && CONFIGFS_FS=3Dm) + 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 }; =20 /** 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 }; =20 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..f6d22510fdc3a 100644 --- a/kernel/printk/nbcon.c +++ b/kernel/printk/nbcon.c @@ -946,6 +946,20 @@ void nbcon_reacquire_nobuf(struct nbcon_write_context = *wctxt) } EXPORT_SYMBOL_GPL(nbcon_reacquire_nobuf); =20 +#ifdef CONFIG_PRINTK_EXECUTION_CTX +static void wctxt_load_execution_ctx(struct nbcon_write_context *wctxt, + struct printk_message *pmsg) +{ + wctxt->cpu =3D pmsg->cpu; + wctxt->pid =3D pmsg->pid; + memcpy(wctxt->comm, pmsg->comm, sizeof(wctxt->comm)); + static_assert(sizeof(wctxt->comm) =3D=3D sizeof(pmsg->comm)); +} +#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 +1062,8 @@ 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_le= n); =20 + 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..cf6b528610366 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -2131,11 +2131,39 @@ static inline void printk_delay(int level) } } =20 +#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 =3D info->caller_id; + u32 caller_id2 =3D info->caller_id2; + + return caller_id & CALLER_ID_MASK ? caller_id2 : caller_id; +} + +static int printk_info_get_cpu(const struct printk_info *info) +{ + u32 caller_id =3D info->caller_id; + u32 caller_id2 =3D info->caller_id2; + + return ((caller_id & CALLER_ID_MASK ? + caller_id : caller_id2) & ~CALLER_ID_MASK); } +#endif =20 /** * printk_parse_prefix - Parse level and control flags. @@ -2213,6 +2241,28 @@ static u16 printk_sprint(char *text, u16 size, int f= acility, return text_len; } =20 +#ifdef CONFIG_PRINTK_EXECUTION_CTX +static void printk_store_execution_ctx(struct printk_info *info) +{ + info->caller_id2 =3D 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 =3D printk_info_get_cpu(info); + pmsg->pid =3D printk_info_get_pid(info); + memcpy(pmsg->comm, info->comm, sizeof(pmsg->comm)); + static_assert(sizeof(pmsg->comm) =3D=3D sizeof(info->comm)); +} +#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 +2370,7 @@ int vprintk_store(int facility, int level, r.info->caller_id =3D caller_id; if (dev_info) memcpy(&r.info->dev_info, dev_info, sizeof(r.info->dev_info)); + printk_store_execution_ctx(r.info); =20 /* A message without a trailing newline can be continued. */ if (!(flags & LOG_NEWLINE)) @@ -3002,6 +3053,7 @@ bool printk_get_next_message(struct printk_message *p= msg, u64 seq, pmsg->seq =3D r.info->seq; pmsg->dropped =3D r.info->seq - seq; force_con =3D r.info->flags & LOG_FORCE_CON; + pmsg_load_execution_ctx(pmsg, r.info); =20 /* * 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_ringb= uffer.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 =20 struct dev_printk_info dev_info; }; diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index ba36939fda79b..fd54b54dc2230 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. =20 +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 + 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 --=20 2.47.3