Checkpoint switching to per-process locks, in attempt clarify xv6's

locking plan, which is a difficult to understand because ptable lock
protects many invariants.  This implementation has a bug: once in a
while xv6 unlocks a proc lock that is locked by another core.

1 files changed, 4 insertions, 1 deletions

diff --git a/kernel/exec.c b/kernel/exec.c
index c9af395..b21afbb 100644
--- a/kernel/exec.c
+++ b/kernel/exec.c
@@ -2,6 +2,7 @@
 #include "param.h"
 #include "memlayout.h"
 #include "riscv.h"
+#include "spinlock.h"
 #include "proc.h"
 #include "defs.h"
 #include "elf.h"
@@ -19,7 +20,6 @@ exec(char *path, char **argv)
   struct proghdr ph;
   pagetable_t pagetable = 0, oldpagetable;
   struct proc *p = myproc();
-  uint64 oldsz = p->sz;
 
   begin_op();
 
@@ -60,6 +60,9 @@ exec(char *path, char **argv)
   end_op();
   ip = 0;
 
+  p = myproc();
+  uint64 oldsz = p->sz;
+
   // Allocate two pages at the next page boundary.
   // Use the second as the user stack.
   sz = PGROUNDUP(sz);