Locking for the per-process resource limits structure.

- struct plimit includes a mutex to protect a reference count.  The plimit
  structure is treated similarly to struct ucred in that is is always copy
  on write, so having a reference to a structure is sufficient to read from
  it without needing a further lock.
- The proc lock protects the p_limit pointer and must be held while reading
  limits from a process to keep the limit structure from changing out from
  under you while reading from it.
- Various global limits that are ints are not protected by a lock since
  int writes are atomic on all the archs we support and thus a lock
  wouldn't buy us anything.
- All accesses to individual resource limits from a process are abstracted
  behind a simple lim_rlimit(), lim_max(), and lim_cur() API that return
  either an rlimit, or the current or max individual limit of the specified
  resource from a process.
- dosetrlimit() was renamed to kern_setrlimit() to match existing style of
  other similar syscall helper functions.
- The alpha OSF/1 compat layer no longer calls getrlimit() and setrlimit()
  (it didn't used the stackgap when it should have) but uses lim_rlimit()
  and kern_setrlimit() instead.
- The svr4 compat no longer uses the stackgap for resource limits calls,
  but uses lim_rlimit() and kern_setrlimit() instead.
- The ibcs2 compat no longer uses the stackgap for resource limits.  It
  also no longer uses the stackgap for accessing sysctl's for the
  ibcs2_sysconf() syscall but uses kernel_sysctl() instead.  As a result,
  ibcs2_sysconf() no longer needs Giant.
- The p_rlimit macro no longer exists.

Submitted by:	mtm (mostly, I only did a few cleanups and catchups)
Tested on:	i386
Compiled on:	alpha, amd64

1 files changed, 8 insertions, 6 deletions

diff --git a/sys/vm/vm_glue.c b/sys/vm/vm_glue.c
index 6fe4405..15d0fd5 100644
--- a/sys/vm/vm_glue.c
+++ b/sys/vm/vm_glue.c
@@ -682,6 +682,7 @@ vm_init_limits(udata)
 	void *udata;
 {
 	struct proc *p = udata;
+	struct plimit *limp;
 	int rss_limit;
 
 	/*
@@ -691,14 +692,15 @@ vm_init_limits(udata)
 	 * of memory - half of main memory helps to favor smaller processes,
 	 * and reduces thrashing of the object cache.
 	 */
-	p->p_rlimit[RLIMIT_STACK].rlim_cur = dflssiz;
-	p->p_rlimit[RLIMIT_STACK].rlim_max = maxssiz;
-	p->p_rlimit[RLIMIT_DATA].rlim_cur = dfldsiz;
-	p->p_rlimit[RLIMIT_DATA].rlim_max = maxdsiz;
+	limp = p->p_limit;
+	limp->pl_rlimit[RLIMIT_STACK].rlim_cur = dflssiz;
+	limp->pl_rlimit[RLIMIT_STACK].rlim_max = maxssiz;
+	limp->pl_rlimit[RLIMIT_DATA].rlim_cur = dfldsiz;
+	limp->pl_rlimit[RLIMIT_DATA].rlim_max = maxdsiz;
 	/* limit the limit to no less than 2MB */
 	rss_limit = max(cnt.v_free_count, 512);
-	p->p_rlimit[RLIMIT_RSS].rlim_cur = ptoa(rss_limit);
-	p->p_rlimit[RLIMIT_RSS].rlim_max = RLIM_INFINITY;
+	limp->pl_rlimit[RLIMIT_RSS].rlim_cur = ptoa(rss_limit);
+	limp->pl_rlimit[RLIMIT_RSS].rlim_max = RLIM_INFINITY;
 }
 
 void