Konstantin Demin
c3d09a3e94
imported from https://salsa.debian.org/kernel-team/linux.git commit 9d5cc9d9d6501d7f1dd7e194d4b245bd0b6c6a22 version 6.11.4-1
83 lines
2.8 KiB
Diff
83 lines
2.8 KiB
Diff
From: John Ogness <john.ogness@linutronix.de>
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Date: Tue, 20 Aug 2024 08:35:47 +0206
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Subject: [PATCH 21/54] printk: Track registered boot consoles
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.11/older/patches-6.11-rt7.tar.xz
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Unfortunately it is not known if a boot console and a regular
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(legacy or nbcon) console use the same hardware. For this reason
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they must not be allowed to print simultaneously.
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For legacy consoles this is not an issue because they are
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already synchronized with the boot consoles using the console
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lock. However nbcon consoles can be triggered separately.
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Add a global flag @have_boot_console to identify if any boot
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consoles are registered. This will be used in follow-up commits
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to ensure that boot consoles and nbcon consoles cannot print
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simultaneously.
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Signed-off-by: John Ogness <john.ogness@linutronix.de>
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Reviewed-by: Petr Mladek <pmladek@suse.com>
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Link: https://lore.kernel.org/r/20240820063001.36405-22-john.ogness@linutronix.de
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Signed-off-by: Petr Mladek <pmladek@suse.com>
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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---
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kernel/printk/printk.c | 24 ++++++++++++++++++++++++
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1 file changed, 24 insertions(+)
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--- a/kernel/printk/printk.c
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+++ b/kernel/printk/printk.c
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@@ -463,6 +463,14 @@ static int console_msg_format = MSG_FORM
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/* syslog_lock protects syslog_* variables and write access to clear_seq. */
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static DEFINE_MUTEX(syslog_lock);
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+/*
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+ * Specifies if a boot console is registered. If boot consoles are present,
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+ * nbcon consoles cannot print simultaneously and must be synchronized by
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+ * the console lock. This is because boot consoles and nbcon consoles may
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+ * have mapped the same hardware.
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+ */
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+static bool have_boot_console;
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+
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#ifdef CONFIG_PRINTK
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DECLARE_WAIT_QUEUE_HEAD(log_wait);
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/* All 3 protected by @syslog_lock. */
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@@ -3611,6 +3619,9 @@ void register_console(struct console *ne
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newcon->seq = init_seq;
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}
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+ if (newcon->flags & CON_BOOT)
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+ have_boot_console = true;
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+
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/*
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* If another context is actively using the hardware of this new
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* console, it will not be aware of the nbcon synchronization. This
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@@ -3681,7 +3692,9 @@ EXPORT_SYMBOL(register_console);
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static int unregister_console_locked(struct console *console)
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{
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bool use_device_lock = (console->flags & CON_NBCON) && console->write_atomic;
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+ bool found_boot_con = false;
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unsigned long flags;
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+ struct console *c;
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int res;
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lockdep_assert_console_list_lock_held();
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@@ -3739,6 +3752,17 @@ static int unregister_console_locked(str
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if (console->exit)
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res = console->exit(console);
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+ /*
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+ * With this console gone, the global flags tracking registered
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+ * console types may have changed. Update them.
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+ */
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+ for_each_console(c) {
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+ if (c->flags & CON_BOOT)
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+ found_boot_con = true;
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+ }
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+ if (!found_boot_con)
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+ have_boot_console = found_boot_con;
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+
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return res;
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}
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