Read curproc from cpu structure, but be careful because after a schedule event

myproc() points to a different thread.

   myproc();
   sched();
   myproc();  // this proc maybe different than the one before sched

Thus, in a function that operates on one thread better to retrieve the
current process once at the start of the function.

1 files changed, 7 insertions, 5 deletions

diff --git a/sysfile.c b/sysfile.c
index fae6960..87e508b 100644
--- a/sysfile.c
+++ b/sysfile.c
@@ -41,10 +41,11 @@ static int
 fdalloc(struct file *f)
 {
   int fd;
+  struct proc *curproc = myproc();
 
   for(fd = 0; fd < NOFILE; fd++){
-    if(myproc()->ofile[fd] == 0){
-      myproc()->ofile[fd] = f;
+    if(curproc->ofile[fd] == 0){
+      curproc->ofile[fd] = f;
       return fd;
     }
   }
@@ -373,7 +374,8 @@ sys_chdir(void)
 {
   char *path;
   struct inode *ip;
-
+  struct proc *curproc = myproc();
+  
   begin_op();
   if(argstr(0, &path) < 0 || (ip = namei(path)) == 0){
     end_op();
@@ -386,9 +388,9 @@ sys_chdir(void)
     return -1;
   }
   iunlock(ip);
-  iput(myproc()->cwd);
+  iput(curproc->cwd);
   end_op();
-  myproc()->cwd = ip;
+  curproc->cwd = ip;
   return 0;
 }