From nobody Thu Dec 18 05:58:35 2025 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 BDC801D6C48 for ; Wed, 4 Sep 2024 12:05:39 +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=1725451541; cv=none; b=geuQPuwjcMlGZlOEka8LC1nHCszSo4sHGHFG8YbKGnN2E65DCNB4acnnBO2bOqpx/7ojWUhL/OXwpZddQ5Ye4ai7rq1tQaCiQz5RFW1WRbEKTKIugXZ+DmMx50O8WNgC+vVdRdL179BqlrfcLM2r7uykyhG4j1Y6VNNjTqqQpSI= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1725451541; c=relaxed/simple; bh=RrReenFUhfTNr3w7bbASYlY5ocUTouRIzthzq0CXPbw=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=m3ri+1D2JETrzegLQZDcrP+9QCZbojKhR20HryPymT179DCzWwkpZ+7wFwsGsUX2Ds+lqGwIC7A2RWR03iWtvmfrPMDMwG0B/SR4SKWWCFoHOQWL4wSpOL0mSsBLBYuDI0Z/f3+AJfN16SMCEl4vvYd2ZoKEFwxfyN5AENPgtp8= 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=pru0TQq4; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=cvUkisJ5; 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="pru0TQq4"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="cvUkisJ5" From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1725451538; 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=37MXrnqoeJsVYXjVaOEeuGP3aysXis+jCd7SmDa0irI=; b=pru0TQq4x0GkA8GuOJzproiWawlQoRjp0i6pnajsy0uwAzPRNtPfNz63icligALv0hvxRU R4yIbDOiUZ0G44KLfrNfJl0daze9qBTCqaeaprYbEq9zjsWJ1V4tKnQzsi606mCMDzHQMJ CQXYHjDjnfOlf33ov6Jx9J3UWIx3jbe35DZFLWmjm7CYatC//rZYeeNE3HIYUQ+BwDJu0S o6Csp43B0ucBQP3Z7vd3VsimpotG+/5vZqhdQw7vUt8CTTOfUMud92xAiqowGzC+MxPVXQ +FX7EgCTLH0QXRcNCf4f4nEhLVeNs8AmvvWUR/Kq8CNjS4mSebZUGuzOON/ykg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1725451538; 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=37MXrnqoeJsVYXjVaOEeuGP3aysXis+jCd7SmDa0irI=; b=cvUkisJ5okf+t34UQpvgHVsLie3SslbiFkbWMsrZE8MCTsAWQBO2hEPqBRYtjZlcGO9V1G G0AdXogS4FcekiAg== To: Petr Mladek Cc: Sergey Senozhatsky , Steven Rostedt , Thomas Gleixner , linux-kernel@vger.kernel.org Subject: [PATCH printk v6 04/17] printk: nbcon: Add context to usable() and emit() Date: Wed, 4 Sep 2024 14:11:23 +0206 Message-Id: <20240904120536.115780-5-john.ogness@linutronix.de> In-Reply-To: <20240904120536.115780-1-john.ogness@linutronix.de> References: <20240904120536.115780-1-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" The nbcon consoles will have two callbacks to be used for different contexts. In order to determine if an nbcon console is usable, console_is_usable() must know if it is a context that will need to use the optional write_atomic() callback. Also, nbcon_emit_next_record() must know which callback it needs to call. Add an extra parameter @use_atomic to console_is_usable() and nbcon_emit_next_record() to specify this. Since so far only the write_atomic() callback exists, @use_atomic is set to true for all call sites. For legacy consoles, @use_atomic is not used. Signed-off-by: John Ogness Reviewed-by: Petr Mladek --- kernel/printk/internal.h | 8 +++++--- kernel/printk/nbcon.c | 34 +++++++++++++++++++--------------- kernel/printk/printk.c | 6 +++--- 3 files changed, 27 insertions(+), 21 deletions(-) diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h index 8e36d8695f81..ad631824e7e5 100644 --- a/kernel/printk/internal.h +++ b/kernel/printk/internal.h @@ -97,7 +97,7 @@ bool nbcon_legacy_emit_next_record(struct console *con, b= ool *handover, * 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) +static inline bool console_is_usable(struct console *con, short flags, boo= l use_atomic) { if (!(flags & CON_ENABLED)) return false; @@ -106,7 +106,8 @@ static inline bool console_is_usable(struct console *co= n, short flags) return false; =20 if (flags & CON_NBCON) { - if (!con->write_atomic) + /* The write_atomic() callback is optional. */ + if (use_atomic && !con->write_atomic) return false; } else { if (!con->write) @@ -149,7 +150,8 @@ static inline void nbcon_atomic_flush_pending(void) { } static inline bool nbcon_legacy_emit_next_record(struct console *con, bool= *handover, int cookie) { return false; } =20 -static inline bool console_is_usable(struct console *con, short flags) { r= eturn false; } +static inline bool console_is_usable(struct console *con, short flags, + bool use_atomic) { return false; } =20 #endif /* CONFIG_PRINTK */ =20 diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c index 8a1bf6f94bce..88db24f9a8de 100644 --- a/kernel/printk/nbcon.c +++ b/kernel/printk/nbcon.c @@ -922,6 +922,7 @@ EXPORT_SYMBOL_GPL(nbcon_reacquire_nobuf); /** * nbcon_emit_next_record - Emit a record in the acquired context * @wctxt: The write context that will be handed to the write function + * @use_atomic: True if the write_atomic() callback is to be used * * Return: True if this context still owns the console. False if * ownership was handed over or taken. @@ -935,7 +936,7 @@ EXPORT_SYMBOL_GPL(nbcon_reacquire_nobuf); * When true is returned, @wctxt->ctxt.backlog indicates whether there are * still records pending in the ringbuffer, */ -static bool nbcon_emit_next_record(struct nbcon_write_context *wctxt) +static bool nbcon_emit_next_record(struct nbcon_write_context *wctxt, bool= use_atomic) { struct nbcon_context *ctxt =3D &ACCESS_PRIVATE(wctxt, ctxt); struct console *con =3D ctxt->console; @@ -946,6 +947,18 @@ static bool nbcon_emit_next_record(struct nbcon_write_= context *wctxt) unsigned long con_dropped; unsigned long dropped; =20 + /* + * This function should never be called for consoles that have not + * implemented the necessary callback for writing: i.e. legacy + * consoles and, when atomic, nbcon consoles with no write_atomic(). + * Handle it as if ownership was lost and try to continue. + */ + if (WARN_ON_ONCE((use_atomic && !con->write_atomic) || + !(console_srcu_read_flags(con) & CON_NBCON))) { + nbcon_context_release(ctxt); + return false; + } + /* * The printk buffers are filled within an unsafe section. This * prevents NBCON_PRIO_NORMAL and NBCON_PRIO_EMERGENCY from @@ -980,17 +993,8 @@ static bool nbcon_emit_next_record(struct nbcon_write_= context *wctxt) /* Initialize the write context for driver callbacks. */ nbcon_write_context_set_buf(wctxt, &pmsg.pbufs->outbuf[0], pmsg.outbuf_le= n); =20 - if (con->write_atomic) { + if (use_atomic) con->write_atomic(con, wctxt); - } else { - /* - * This function should never be called for legacy consoles. - * Handle it as if ownership was lost and try to continue. - */ - WARN_ON_ONCE(1); - nbcon_context_release(ctxt); - return false; - } =20 if (!wctxt->outbuf) { /* @@ -1118,7 +1122,7 @@ static bool nbcon_atomic_emit_one(struct nbcon_write_= context *wctxt) * The higher priority printing context takes over responsibility * to print the pending records. */ - if (!nbcon_emit_next_record(wctxt)) + if (!nbcon_emit_next_record(wctxt, true)) return false; =20 nbcon_context_release(ctxt); @@ -1219,7 +1223,7 @@ static int __nbcon_atomic_flush_pending_con(struct co= nsole *con, u64 stop_seq, * handed over or taken over. In both cases the context is no * longer valid. */ - if (!nbcon_emit_next_record(&wctxt)) + if (!nbcon_emit_next_record(&wctxt, true)) return -EAGAIN; =20 if (!ctxt->backlog) { @@ -1305,7 +1309,7 @@ static void __nbcon_atomic_flush_pending(u64 stop_seq= , bool allow_unsafe_takeove if (!(flags & CON_NBCON)) continue; =20 - if (!console_is_usable(con, flags)) + if (!console_is_usable(con, flags, true)) continue; =20 if (nbcon_seq_read(con) >=3D stop_seq) @@ -1490,7 +1494,7 @@ void nbcon_device_release(struct console *con) * the console is usable throughout flushing. */ cookie =3D console_srcu_read_lock(); - if (console_is_usable(con, console_srcu_read_flags(con)) && + if (console_is_usable(con, console_srcu_read_flags(con), true) && prb_read_valid(prb, nbcon_seq_read(con), NULL)) { /* * If nbcon_atomic flushing is not available, fallback to diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index c79e962b822a..846306ac2663 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -3071,7 +3071,7 @@ static bool console_flush_all(bool do_cond_resched, u= 64 *next_seq, bool *handove u64 printk_seq; bool progress; =20 - if (!console_is_usable(con, flags)) + if (!console_is_usable(con, flags, true)) continue; any_usable =3D true; =20 @@ -3773,7 +3773,7 @@ static int unregister_console_locked(struct console *= console) =20 if (!console_is_registered_locked(console)) res =3D -ENODEV; - else if (console_is_usable(console, console->flags)) + else if (console_is_usable(console, console->flags, true)) __pr_flush(console, 1000, true); =20 /* Disable it unconditionally */ @@ -4043,7 +4043,7 @@ static bool __pr_flush(struct console *con, int timeo= ut_ms, bool reset_on_progre * that they make forward progress, so only increment * @diff for usable consoles. */ - if (!console_is_usable(c, flags)) + if (!console_is_usable(c, flags, true)) continue; =20 if (flags & CON_NBCON) { --=20 2.39.2