Konstantin Demin
c3d09a3e94
imported from https://salsa.debian.org/kernel-team/linux.git commit 9d5cc9d9d6501d7f1dd7e194d4b245bd0b6c6a22 version 6.11.4-1
69 lines
2.5 KiB
Diff
69 lines
2.5 KiB
Diff
From: John Ogness <john.ogness@linutronix.de>
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Date: Tue, 20 Aug 2024 08:35:49 +0206
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Subject: [PATCH 23/54] printk: Add is_printk_legacy_deferred()
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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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If printk has been explicitly deferred or is called from NMI
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context, legacy console printing must be deferred to an irq_work
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context. Introduce a helper function is_printk_legacy_deferred()
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for a CPU to query if it must defer legacy console printing.
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In follow-up commits this helper will be needed at other call
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sites as well.
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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/20240820063001.36405-24-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/internal.h | 2 ++
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kernel/printk/printk_safe.c | 11 ++++++++++-
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2 files changed, 12 insertions(+), 1 deletion(-)
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--- a/kernel/printk/internal.h
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+++ b/kernel/printk/internal.h
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@@ -75,6 +75,7 @@ bool printk_percpu_data_ready(void);
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} while (0)
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void defer_console_output(void);
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+bool is_printk_legacy_deferred(void);
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u16 printk_parse_prefix(const char *text, int *level,
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enum printk_info_flags *flags);
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@@ -138,6 +139,7 @@ static inline bool console_is_usable(str
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#define printk_safe_exit_irqrestore(flags) local_irq_restore(flags)
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static inline bool printk_percpu_data_ready(void) { return false; }
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+static inline bool is_printk_legacy_deferred(void) { return false; }
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static inline u64 nbcon_seq_read(struct console *con) { return 0; }
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static inline void nbcon_seq_force(struct console *con, u64 seq) { }
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static inline bool nbcon_alloc(struct console *con) { return false; }
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--- a/kernel/printk/printk_safe.c
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+++ b/kernel/printk/printk_safe.c
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@@ -38,6 +38,15 @@ void __printk_deferred_exit(void)
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__printk_safe_exit();
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}
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+bool is_printk_legacy_deferred(void)
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+{
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+ /*
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+ * The per-CPU variable @printk_context can be read safely in any
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+ * context. CPU migration is always disabled when set.
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+ */
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+ return (this_cpu_read(printk_context) || in_nmi());
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+}
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+
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asmlinkage int vprintk(const char *fmt, va_list args)
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{
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#ifdef CONFIG_KGDB_KDB
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@@ -50,7 +59,7 @@ asmlinkage int vprintk(const char *fmt,
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* Use the main logbuf even in NMI. But avoid calling console
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* drivers that might have their own locks.
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*/
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- if (this_cpu_read(printk_context) || in_nmi())
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+ if (is_printk_legacy_deferred())
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return vprintk_deferred(fmt, args);
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/* No obstacles. */
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