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Diffstat (limited to 'kernel/printk/printk_safe.c')
-rw-r--r--kernel/printk/printk_safe.c26
1 files changed, 24 insertions, 2 deletions
diff --git a/kernel/printk/printk_safe.c b/kernel/printk/printk_safe.c
index 033e50a7d706..03a42a539b20 100644
--- a/kernel/printk/printk_safe.c
+++ b/kernel/printk/printk_safe.c
@@ -308,12 +308,24 @@ static int vprintk_nmi(const char *fmt, va_list args)
void printk_nmi_enter(void)
{
- this_cpu_or(printk_context, PRINTK_NMI_CONTEXT_MASK);
+ /*
+ * The size of the extra per-CPU buffer is limited. Use it only when
+ * the main one is locked. If this CPU is not in the safe context,
+ * the lock must be taken on another CPU and we could wait for it.
+ */
+ if ((this_cpu_read(printk_context) & PRINTK_SAFE_CONTEXT_MASK) &&
+ raw_spin_is_locked(&logbuf_lock)) {
+ this_cpu_or(printk_context, PRINTK_NMI_CONTEXT_MASK);
+ } else {
+ this_cpu_or(printk_context, PRINTK_NMI_DEFERRED_CONTEXT_MASK);
+ }
}
void printk_nmi_exit(void)
{
- this_cpu_and(printk_context, ~PRINTK_NMI_CONTEXT_MASK);
+ this_cpu_and(printk_context,
+ ~(PRINTK_NMI_CONTEXT_MASK |
+ PRINTK_NMI_DEFERRED_CONTEXT_MASK));
}
#else
@@ -351,12 +363,22 @@ void __printk_safe_exit(void)
__printf(1, 0) int vprintk_func(const char *fmt, va_list args)
{
+ /* Use extra buffer in NMI when logbuf_lock is taken or in safe mode. */
if (this_cpu_read(printk_context) & PRINTK_NMI_CONTEXT_MASK)
return vprintk_nmi(fmt, args);
+ /* Use extra buffer to prevent a recursion deadlock in safe mode. */
if (this_cpu_read(printk_context) & PRINTK_SAFE_CONTEXT_MASK)
return vprintk_safe(fmt, args);
+ /*
+ * Use the main logbuf when logbuf_lock is available in NMI.
+ * But avoid calling console drivers that might have their own locks.
+ */
+ if (this_cpu_read(printk_context) & PRINTK_NMI_DEFERRED_CONTEXT_MASK)
+ return vprintk_deferred(fmt, args);
+
+ /* No obstacles. */
return vprintk_default(fmt, args);
}