From b63d3506e9fbe7db1cd117db746fb58b7712ab4f Mon Sep 17 00:00:00 2001
From: Frans Kaashoek <kaashoek@mit.edu>
Date: Thu, 5 Nov 2020 11:09:21 -0500
Subject: [PATCH] Be principled: acquire lock first

---
 kernel/log.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/log.c b/kernel/log.c
index c8af5bd..2c0063a 100644
--- a/kernel/log.c
+++ b/kernel/log.c
@@ -216,12 +216,12 @@ log_write(struct buf *b)
 {
   int i;
 
+  acquire(&log.lock);
   if (log.lh.n >= LOGSIZE || log.lh.n >= log.size - 1)
     panic("too big a transaction");
   if (log.outstanding < 1)
     panic("log_write outside of trans");
 
-  acquire(&log.lock);
   for (i = 0; i < log.lh.n; i++) {
     if (log.lh.block[i] == b->blockno)   // log absorbtion
       break;