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https://github.com/linux-msm/laptops-kernel.git
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John Ogness
93d102f094
With @logbuf_lock removed, the high level printk functions for storing messages are lockless. Messages can be stored from any context, so there is no need for the NMI and safe buffers anymore. Remove the NMI and safe buffers. Although the safe buffers are removed, the NMI and safe context tracking is still in place. In these contexts, store the message immediately but still use irq_work to defer the console printing. Since printk recursion tracking is in place, safe context tracking for most of printk is not needed. Remove it. Only safe context tracking relating to the console and console_owner locks is left in place. This is because the console and console_owner locks are needed for the actual printing. Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20210715193359.25946-4-john.ogness@linutronix.de
88 lines
2.0 KiB
C
88 lines
2.0 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* printk_safe.c - Safe printk for printk-deadlock-prone contexts
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*/
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#include <linux/preempt.h>
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#include <linux/spinlock.h>
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#include <linux/debug_locks.h>
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#include <linux/kdb.h>
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#include <linux/smp.h>
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#include <linux/cpumask.h>
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#include <linux/irq_work.h>
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#include <linux/printk.h>
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#include <linux/kprobes.h>
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#include "internal.h"
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static DEFINE_PER_CPU(int, printk_context);
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#ifdef CONFIG_PRINTK_NMI
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void noinstr printk_nmi_enter(void)
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{
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this_cpu_add(printk_context, PRINTK_NMI_CONTEXT_OFFSET);
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}
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void noinstr printk_nmi_exit(void)
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{
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this_cpu_sub(printk_context, PRINTK_NMI_CONTEXT_OFFSET);
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}
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/*
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* Marks a code that might produce many messages in NMI context
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* and the risk of losing them is more critical than eventual
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* reordering.
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*/
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void printk_nmi_direct_enter(void)
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{
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if (this_cpu_read(printk_context) & PRINTK_NMI_CONTEXT_MASK)
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this_cpu_or(printk_context, PRINTK_NMI_DIRECT_CONTEXT_MASK);
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}
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void printk_nmi_direct_exit(void)
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{
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this_cpu_and(printk_context, ~PRINTK_NMI_DIRECT_CONTEXT_MASK);
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}
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#endif /* CONFIG_PRINTK_NMI */
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/* Can be preempted by NMI. */
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void __printk_safe_enter(void)
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{
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this_cpu_inc(printk_context);
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}
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/* Can be preempted by NMI. */
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void __printk_safe_exit(void)
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{
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this_cpu_dec(printk_context);
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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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/* Allow to pass printk() to kdb but avoid a recursion. */
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if (unlikely(kdb_trap_printk && kdb_printf_cpu < 0))
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return vkdb_printf(KDB_MSGSRC_PRINTK, fmt, args);
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#endif
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/*
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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) &
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(PRINTK_NMI_DIRECT_CONTEXT_MASK |
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PRINTK_NMI_CONTEXT_MASK |
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PRINTK_SAFE_CONTEXT_MASK)) {
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int len;
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len = vprintk_store(0, LOGLEVEL_DEFAULT, NULL, fmt, args);
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defer_console_output();
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return len;
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}
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/* No obstacles. */
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return vprintk_default(fmt, args);
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}
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EXPORT_SYMBOL(vprintk);
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