From nobody Sun Feb 8 04:12:46 2026 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (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 01BD32F90D3; Tue, 11 Nov 2025 14:43:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762872215; cv=none; b=FTNsbRlR1t7YkjFAs9bs5rOUGEAObVkmkgYqFig9RoVya+GOweAl0aU29lORDFwFwG08EkzapmXOgUvm1qywPAgNTJHbfF912y1NYLEjNH/Uwn/1eHwSeSUAswBFt3Uk0iVIGpo48lEGfy1b7OsN/9jnelF26gvul+rAIELt4pc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762872215; c=relaxed/simple; bh=MPu/tsOZkT6J35VS9D16ketf3w7CW09xPX2aNv8BGiY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=nWMNga5HzQ0KxCpi5GT5Kq2mE8HPeregMfntGGYI565RKnwK/MFvT98MtjhLJOC6iyst8foEXV/yRuS80pBgvFLx6iQ7gucKCfSkmK15cXAYpKRhJnSRSEvtYYC3qMa/bGi+CF3F2gxH0Qpoocr/zadAznYSqsNZuD42+XJaFxA= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=XOV4ic+H; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=0+KZeCa2; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="XOV4ic+H"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="0+KZeCa2" From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1762872211; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=b91XU7hHkSIra6MHumO32Fr5vsRcsLrtiPH/XTCjqNI=; b=XOV4ic+HXGvqHQaprQ+1Wiqu+OhiPXmHsNT4NZD5vuxD+6+2qpDs0gVoTGmMkrz0nFCxsm BE7hRRmz62S4ha7qQ+bNOM6MgQybVTUs7IPqL0LRZU+LoIEKBWvoIVVmmkm6sWvdJVD5UF taaynjfUH2OV53hlSeHrgXABcQoYOeQ+2LNvvNK+LkPgW0hkZsvtMfHG1fQ2Ug3WSlqPhw LpjRRfViaSMh7OqOJ+G0ZIk7wZ6nc6wo4vbI7YmIKWnWt4cL2zD/y/z1wB1yEoX+lvkVHF JaXZS9PnWi8FK3kEBAw1Knx+SI5qXzvyaM2itb8zOLkob+ZA5aX64XSuxI5TCw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1762872211; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=b91XU7hHkSIra6MHumO32Fr5vsRcsLrtiPH/XTCjqNI=; b=0+KZeCa2N9RV08W4UvShLECsB/34rtVclgZKmAJoNTZzLDul+ENaUGLa3rbKWPcW2irJeS C+2O1yZemBx/VFCg== To: Petr Mladek Cc: Sergey Senozhatsky , Steven Rostedt , Sherry Sun , Jacky Bai , Jon Hunter , Thierry Reding , Derek Barbosa , linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH printk v1 1/1] printk: Avoid scheduling irq_work on suspend Date: Tue, 11 Nov 2025 15:49:22 +0106 Message-ID: <20251111144328.887159-2-john.ogness@linutronix.de> In-Reply-To: <20251111144328.887159-1-john.ogness@linutronix.de> References: <20251111144328.887159-1-john.ogness@linutronix.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Allowing irq_work to be scheduled while trying to suspend has shown to cause problems as some architectures interpret the pending interrupts as a reason to not suspend. This became a problem for printk() with the introduction of NBCON consoles. With every printk() call, NBCON console printing kthreads are woken by queueing irq_work. This means that irq_work continues to be queued due to printk() calls late in the suspend procedure. Avoid this problem by preventing printk() from queueing irq_work once console suspending has begun. This applies to triggering NBCON and legacy deferred printing as well as klogd waiters. Since triggering of NBCON threaded printing relies on irq_work, the pr_flush() within console_suspend_all() is used to perform the final flushing before suspending consoles and blocking irq_work queueing. NBCON consoles that are not suspended (due to the usage of the "no_console_suspend" boot argument) transition to atomic flushing. Introduce a new global variable @console_offload_blocked to flag when irq_work queueing is to be avoided. The flag is used by printk_get_console_flush_type() to avoid allowing deferred printing and switch NBCON consoles to atomic flushing. It is also used by vprintk_emit() to avoid klogd waking. Cc: # 6.13.x because no drivers in 6.12.x Fixes: 6b93bb41f6ea ("printk: Add non-BKL (nbcon) console basic infrastruct= ure") Closes: https://lore.kernel.org/lkml/DB9PR04MB8429E7DDF2D93C2695DE401D92C4A= @DB9PR04MB8429.eurprd04.prod.outlook.com Signed-off-by: John Ogness --- kernel/printk/internal.h | 8 ++++--- kernel/printk/printk.c | 51 ++++++++++++++++++++++++++++------------ 2 files changed, 41 insertions(+), 18 deletions(-) diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h index f72bbfa266d6c..b20929b7d71f5 100644 --- a/kernel/printk/internal.h +++ b/kernel/printk/internal.h @@ -230,6 +230,8 @@ struct console_flush_type { bool legacy_offload; }; =20 +extern bool console_irqwork_blocked; + /* * Identify which console flushing methods should be used in the context of * the caller. @@ -241,7 +243,7 @@ static inline void printk_get_console_flush_type(struct= console_flush_type *ft) switch (nbcon_get_default_prio()) { case NBCON_PRIO_NORMAL: if (have_nbcon_console && !have_boot_console) { - if (printk_kthreads_running) + if (printk_kthreads_running && !console_irqwork_blocked) ft->nbcon_offload =3D true; else ft->nbcon_atomic =3D true; @@ -251,7 +253,7 @@ static inline void printk_get_console_flush_type(struct= console_flush_type *ft) if (have_legacy_console || have_boot_console) { if (!is_printk_legacy_deferred()) ft->legacy_direct =3D true; - else + else if (!console_irqwork_blocked) ft->legacy_offload =3D true; } break; @@ -264,7 +266,7 @@ static inline void printk_get_console_flush_type(struct= console_flush_type *ft) if (have_legacy_console || have_boot_console) { if (!is_printk_legacy_deferred()) ft->legacy_direct =3D true; - else + else if (!console_irqwork_blocked) ft->legacy_offload =3D true; } break; diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 5aee9ffb16b9a..94fc4a8662d4b 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -462,6 +462,9 @@ bool have_boot_console; /* See printk_legacy_allow_panic_sync() for details. */ bool legacy_allow_panic_sync; =20 +/* Avoid using irq_work when suspending. */ +bool console_irqwork_blocked; + #ifdef CONFIG_PRINTK DECLARE_WAIT_QUEUE_HEAD(log_wait); static DECLARE_WAIT_QUEUE_HEAD(legacy_wait); @@ -2426,7 +2429,7 @@ asmlinkage int vprintk_emit(int facility, int level, =20 if (ft.legacy_offload) defer_console_output(); - else + else if (!console_irqwork_blocked) wake_up_klogd(); =20 return printed_len; @@ -2730,10 +2733,20 @@ void console_suspend_all(void) { struct console *con; =20 + if (console_suspend_enabled) + pr_info("Suspending console(s) (use no_console_suspend to debug)\n"); + + /* + * Flush any console backlog and then avoid queueing irq_work until + * console_resume_all(). Until then deferred printing is no longer + * triggered, NBCON consoles transition to atomic flushing, and + * any klogd waiters are not triggered. + */ + pr_flush(1000, true); + console_irqwork_blocked =3D true; + if (!console_suspend_enabled) return; - pr_info("Suspending console(s) (use no_console_suspend to debug)\n"); - pr_flush(1000, true); =20 console_list_lock(); for_each_console(con) @@ -2754,26 +2767,34 @@ void console_resume_all(void) struct console_flush_type ft; struct console *con; =20 - if (!console_suspend_enabled) - return; - - console_list_lock(); - for_each_console(con) - console_srcu_write_flags(con, con->flags & ~CON_SUSPENDED); - console_list_unlock(); - /* - * Ensure that all SRCU list walks have completed. All printing - * contexts must be able to see they are no longer suspended so - * that they are guaranteed to wake up and resume printing. + * Allow queueing irq_work. After restoring console state, deferred + * printing and any klogd waiters need to be triggered in case there + * is now a console backlog. */ - synchronize_srcu(&console_srcu); + console_irqwork_blocked =3D false; + + if (console_suspend_enabled) { + console_list_lock(); + for_each_console(con) + console_srcu_write_flags(con, con->flags & ~CON_SUSPENDED); + console_list_unlock(); + + /* + * Ensure that all SRCU list walks have completed. All printing + * contexts must be able to see they are no longer suspended so + * that they are guaranteed to wake up and resume printing. + */ + synchronize_srcu(&console_srcu); + } =20 printk_get_console_flush_type(&ft); if (ft.nbcon_offload) nbcon_kthreads_wake(); if (ft.legacy_offload) defer_console_output(); + else + wake_up_klogd(); =20 pr_flush(1000, true); } --=20 2.47.3