Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
Merge tag 'printk-for-6.14' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux
Pull printk updates from Petr Mladek:
- Prevent possible deadlocks, caused by the lock serializing per-CPU
backtraces, by entering the deferred printk context
- Enforce the right casting in LOG_BUF_LEN_MAX definition
* tag 'printk-for-6.14' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux:
printk: Defer legacy printing when holding printk_cpu_sync
printk: Remove redundant deferred check in vprintk()
printk: Fix signed integer overflow when defining LOG_BUF_LEN_MAX
+18
-11
+6
kernel/printk/internal.h
+6
kernel/printk/internal.h
···
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void console_prepend_dropped(struct printk_message *pmsg, unsigned long dropped);
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void console_prepend_replay(struct printk_message *pmsg);
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#endif
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+
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+
#ifdef CONFIG_SMP
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+
bool is_printk_cpu_sync_owner(void);
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+
#else
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+
static inline bool is_printk_cpu_sync_owner(void) { return false; }
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+
#endif
+6
-1
kernel/printk/printk.c
+6
-1
kernel/printk/printk.c
···
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523
/* record buffer */
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#define LOG_ALIGN __alignof__(unsigned long)
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#define __LOG_BUF_LEN (1 << CONFIG_LOG_BUF_SHIFT)
526
-
#define LOG_BUF_LEN_MAX (u32)(1 << 31)
526
+
#define LOG_BUF_LEN_MAX ((u32)1 << 31)
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static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
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static char *log_buf = __log_buf;
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static u32 log_buf_len = __LOG_BUF_LEN;
···
4921
4921
#ifdef CONFIG_SMP
4922
4922
static atomic_t printk_cpu_sync_owner = ATOMIC_INIT(-1);
4923
4923
static atomic_t printk_cpu_sync_nested = ATOMIC_INIT(0);
4924
+
4925
+
bool is_printk_cpu_sync_owner(void)
4926
+
{
4927
+
return (atomic_read(&printk_cpu_sync_owner) == raw_smp_processor_id());
4928
+
}
4924
4929
4925
4930
/**
4926
4931
* __printk_cpu_sync_wait() - Busy wait until the printk cpu-reentrant
+6
-10
kernel/printk/printk_safe.c
+6
-10
kernel/printk/printk_safe.c
···
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61
/*
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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.
64
+
*
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+
* A context holding the printk_cpu_sync must not spin waiting for
66
+
* another CPU. For legacy printing, it could be the console_lock
67
+
* or the port lock.
64
68
*/
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return (force_legacy_kthread() ||
66
70
this_cpu_read(printk_context) ||
67
-
in_nmi());
71
+
in_nmi() ||
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+
is_printk_cpu_sync_owner());
68
73
}
69
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asmlinkage int vprintk(const char *fmt, va_list args)
···
79
74
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
82
-
83
-
/*
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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 (is_printk_legacy_deferred())
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-
return vprintk_deferred(fmt, args);
89
-
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-
/* No obstacles. */
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77
return vprintk_default(fmt, args);
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78
}
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EXPORT_SYMBOL(vprintk);