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c=relaxed/relaxed; d=linutronix.de; s=2020; t=1708282673; 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=2WpRiuHUchJ8PUhBQPppc9wlrZ+BaiMWpumcr51nxKc=; b=X1pn8gUlKUoMEiWMnaptlfxcDZ/fGoV6vTRapTZO3rzlah99nQ7MUPx+Ha+jrZN1cvTGZK JrPWwd+KnMJUZjxwwHxTkgZVzelM+KIUL80N/0gM6KtqB55uszHNyVCyXY/pQk0wvOMwkK N6sB+qCR2oVPZG6QvDCPvmLZ57GaYjSgXdCKjpF4NqvFXXlZsZqnR2BmuZf9AIg8n8iGUl S8LlAegzwnddOuEvKG4KlklwB/76QjbzJ5Wyth4ktGSyyjuLFureb94qasBM6jQBt0Zwl7 aOLDzHlfdM2jKBlHAaa6J73DIx02d5aN2C4UQXkBVqFDNc0DtFwIBf7GnVdWRw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1708282673; 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=2WpRiuHUchJ8PUhBQPppc9wlrZ+BaiMWpumcr51nxKc=; b=uRlGqUPmvzNMGbcXT8nTGeSPZO0Nk1Wof15ZY2YyL6MAW1gTwVA2JE+R49msvY6HL7XMAh Ch1jTVfhrX2veLBQ== To: Petr Mladek Cc: Sergey Senozhatsky , Steven Rostedt , Thomas Gleixner , linux-kernel@vger.kernel.org Subject: [PATCH printk v2 16/26] printk: nbcon: Use nbcon consoles in console_flush_all() Date: Sun, 18 Feb 2024 20:03:16 +0106 Message-Id: <20240218185726.1994771-17-john.ogness@linutronix.de> In-Reply-To: <20240218185726.1994771-1-john.ogness@linutronix.de> References: <20240218185726.1994771-1-john.ogness@linutronix.de> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1791264445759991389 X-GMAIL-MSGID: 1791264445759991389 Allow nbcon consoles to print messages in the legacy printk() caller context (printing via unlock) by integrating them into console_flush_all(). The write_atomic() callback is used for printing. Provide nbcon_legacy_emit_next_record(), which acts as the nbcon variant of console_emit_next_record(). Call this variant within console_flush_all() for nbcon consoles. Since nbcon consoles use their own @nbcon_seq variable to track the next record to print, this also must be appropriately handled. Signed-off-by: John Ogness --- kernel/printk/internal.h | 6 ++++++ kernel/printk/nbcon.c | 45 ++++++++++++++++++++++++++++++++++++++++ kernel/printk/printk.c | 19 ++++++++++++----- 3 files changed, 65 insertions(+), 5 deletions(-) diff --git a/kernel/printk/internal.h b/kernel/printk/internal.h index d9a5205692fc..b34847ec6b0d 100644 --- a/kernel/printk/internal.h +++ b/kernel/printk/internal.h @@ -71,6 +71,8 @@ void defer_console_output(void); u16 printk_parse_prefix(const char *text, int *level, enum printk_info_flags *flags); +void console_lock_spinning_enable(void); +int console_lock_spinning_disable_and_check(int cookie); u64 nbcon_seq_read(struct console *con); void nbcon_seq_force(struct console *con, u64 seq); @@ -78,6 +80,8 @@ bool nbcon_alloc(struct console *con); void nbcon_init(struct console *con); void nbcon_free(struct console *con); void nbcon_atomic_flush_all(void); +bool nbcon_legacy_emit_next_record(struct console *con, bool *handover, + int cookie); /* * Check if the given console is currently capable and allowed to print @@ -133,6 +137,8 @@ static inline bool nbcon_alloc(struct console *con) { return false; } static inline void nbcon_init(struct console *con) { } static inline void nbcon_free(struct console *con) { } static inline void nbcon_atomic_flush_all(void) { } +static inline bool nbcon_legacy_emit_next_record(struct console *con, bool *handover, + int cookie) { return false; } static inline bool console_is_usable(struct console *con, short flags) { return false; } diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c index 2eb2929c1027..747f5cbfe5ee 100644 --- a/kernel/printk/nbcon.c +++ b/kernel/printk/nbcon.c @@ -532,6 +532,7 @@ static struct printk_buffers panic_nbcon_pbufs; * nbcon_context_try_acquire - Try to acquire nbcon console * @ctxt: The context of the caller * + * Context: Any context which could not be migrated to another CPU. * Return: True if the console was acquired. False otherwise. * * If the caller allowed an unsafe hostile takeover, on success the @@ -960,6 +961,50 @@ static bool nbcon_atomic_emit_one(struct nbcon_write_context *wctxt) return ctxt->backlog; } +/** + * nbcon_legacy_emit_next_record - Print one record for an nbcon console + * in legacy contexts + * @con: The console to print on + * @handover: Will be set to true if a printk waiter has taken over the + * console_lock, in which case the caller is no longer holding + * both the console_lock and the SRCU read lock. Otherwise it + * is set to false. + * @cookie: The cookie from the SRCU read lock. + * + * Context: Any context which could not be migrated to another CPU. + * Return: True if a record could be printed, otherwise false. + * + * This function is meant to be called by console_flush_all() to print records + * on nbcon consoles from legacy context (printing via console unlocking). + * Essentially it is the nbcon version of console_emit_next_record(). + */ +bool nbcon_legacy_emit_next_record(struct console *con, bool *handover, + int cookie) +{ + struct nbcon_write_context wctxt = { }; + struct nbcon_context *ctxt = &ACCESS_PRIVATE(&wctxt, ctxt); + bool progress = false; + unsigned long flags; + + *handover = false; + + /* Use the same procedure as console_emit_next_record(). */ + printk_safe_enter_irqsave(flags); + console_lock_spinning_enable(); + stop_critical_timings(); + + ctxt->console = con; + ctxt->prio = NBCON_PRIO_NORMAL; + + progress = nbcon_atomic_emit_one(&wctxt); + + start_critical_timings(); + *handover = console_lock_spinning_disable_and_check(cookie); + printk_safe_exit_irqrestore(flags); + + return progress; +} + /** * __nbcon_atomic_flush_all - Flush all nbcon consoles using their * write_atomic() callback diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c index 1b14159990ba..d91771fb306e 100644 --- a/kernel/printk/printk.c +++ b/kernel/printk/printk.c @@ -1871,7 +1871,7 @@ static bool console_waiter; * there may be a waiter spinning (like a spinlock). Also it must be * ready to hand over the lock at the end of the section. */ -static void console_lock_spinning_enable(void) +void console_lock_spinning_enable(void) { /* * Do not use spinning in panic(). The panic CPU wants to keep the lock. @@ -1910,7 +1910,7 @@ static void console_lock_spinning_enable(void) * * Return: 1 if the lock rights were passed, 0 otherwise. */ -static int console_lock_spinning_disable_and_check(int cookie) +int console_lock_spinning_disable_and_check(int cookie) { int waiter; @@ -2948,13 +2948,22 @@ static bool console_flush_all(bool do_cond_resched, u64 *next_seq, bool *handove cookie = console_srcu_read_lock(); for_each_console_srcu(con) { short flags = console_srcu_read_flags(con); + u64 printk_seq; bool progress; if (!console_is_usable(con, flags)) continue; any_usable = true; - progress = console_emit_next_record(con, handover, cookie); + if (flags & CON_NBCON) { + progress = nbcon_legacy_emit_next_record(con, handover, cookie); + + printk_seq = nbcon_seq_read(con); + } else { + progress = console_emit_next_record(con, handover, cookie); + + printk_seq = con->seq; + } /* * If a handover has occurred, the SRCU read lock @@ -2964,8 +2973,8 @@ static bool console_flush_all(bool do_cond_resched, u64 *next_seq, bool *handove return false; /* Track the next of the highest seq flushed. */ - if (con->seq > *next_seq) - *next_seq = con->seq; + if (printk_seq > *next_seq) + *next_seq = printk_seq; if (!progress) continue;