pstore: Avoid recursive spinlocks in the oops_in_progress case

Like 8250 driver, when pstore is registered as a console,
to avoid recursive spinlocks when panic happening, change the
spin_lock_irqsave to spin_trylock_irqsave when oops_in_progress
is true.
Signed-off-by: liu chuansheng <chuansheng.liu@intel.com>
Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>

fs/pstore/platform.c

@@ -164,7 +164,13 @@ static void pstore_console_write(struct console *con, const char *s, unsigned c)
 
 		if (c > psinfo->bufsize)
 			c = psinfo->bufsize;
-		spin_lock_irqsave(&psinfo->buf_lock, flags);
+
+		if (oops_in_progress) {
+			if (!spin_trylock_irqsave(&psinfo->buf_lock, flags))
+				break;
+		} else {
+			spin_lock_irqsave(&psinfo->buf_lock, flags);
+		}
 		memcpy(psinfo->buf, s, c);
 		psinfo->write(PSTORE_TYPE_CONSOLE, 0, NULL, 0, c, psinfo);
 		spin_unlock_irqrestore(&psinfo->buf_lock, flags);