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-rw-r--r--kernel/printk.c13
1 files changed, 12 insertions, 1 deletions
diff --git a/kernel/printk.c b/kernel/printk.c
index 5092397..a967605 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -514,6 +514,9 @@ asmlinkage int printk(const char *fmt, ...)
return r;
}
+/* cpu currently holding logbuf_lock */
+static volatile unsigned int printk_cpu = UINT_MAX;
+
asmlinkage int vprintk(const char *fmt, va_list args)
{
unsigned long flags;
@@ -522,11 +525,15 @@ asmlinkage int vprintk(const char *fmt, va_list args)
static char printk_buf[1024];
static int log_level_unknown = 1;
- if (unlikely(oops_in_progress))
+ preempt_disable();
+ if (unlikely(oops_in_progress) && printk_cpu == smp_processor_id())
+ /* If a crash is occurring during printk() on this CPU,
+ * make sure we can't deadlock */
zap_locks();
/* This stops the holder of console_sem just where we want him */
spin_lock_irqsave(&logbuf_lock, flags);
+ printk_cpu = smp_processor_id();
/* Emit the output into the temporary buffer */
printed_len = vscnprintf(printk_buf, sizeof(printk_buf), fmt, args);
@@ -595,6 +602,7 @@ asmlinkage int vprintk(const char *fmt, va_list args)
* CPU until it is officially up. We shouldn't be calling into
* random console drivers on a CPU which doesn't exist yet..
*/
+ printk_cpu = UINT_MAX;
spin_unlock_irqrestore(&logbuf_lock, flags);
goto out;
}
@@ -604,6 +612,7 @@ asmlinkage int vprintk(const char *fmt, va_list args)
* We own the drivers. We can drop the spinlock and let
* release_console_sem() print the text
*/
+ printk_cpu = UINT_MAX;
spin_unlock_irqrestore(&logbuf_lock, flags);
console_may_schedule = 0;
release_console_sem();
@@ -613,9 +622,11 @@ asmlinkage int vprintk(const char *fmt, va_list args)
* allows the semaphore holder to proceed and to call the
* console drivers with the output which we just produced.
*/
+ printk_cpu = UINT_MAX;
spin_unlock_irqrestore(&logbuf_lock, flags);
}
out:
+ preempt_enable();
return printed_len;
}
EXPORT_SYMBOL(printk);
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