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, 11 insertions, 13 deletions

diff --git a/sys/kern/init_main.c b/sys/kern/init_main.c
index 7128835..4e91f64 100644
--- a/sys/kern/init_main.c
+++ b/sys/kern/init_main.c
@@ -93,7 +93,6 @@ struct	thread thread0;
 struct	kse kse0;
 struct	ksegrp ksegrp0;
 static struct filedesc0 filedesc0;
-static struct plimit limit0;
 struct	vmspace vmspace0;
 struct	proc *initproc;
 
@@ -419,19 +418,18 @@ proc0_init(void *dummy __unused)
 	fdp->fd_fd.fd_map = fdp->fd_dmap;
 
 	/* Create the limits structures. */
-	p->p_limit = &limit0;
-	for (i = 0; i < sizeof(p->p_rlimit)/sizeof(p->p_rlimit[0]); i++)
-		limit0.pl_rlimit[i].rlim_cur =
-		    limit0.pl_rlimit[i].rlim_max = RLIM_INFINITY;
-	limit0.pl_rlimit[RLIMIT_NOFILE].rlim_cur =
-	    limit0.pl_rlimit[RLIMIT_NOFILE].rlim_max = maxfiles;
-	limit0.pl_rlimit[RLIMIT_NPROC].rlim_cur =
-	    limit0.pl_rlimit[RLIMIT_NPROC].rlim_max = maxproc;
+	p->p_limit = lim_alloc();
+	for (i = 0; i < RLIM_NLIMITS; i++)
+		p->p_limit->pl_rlimit[i].rlim_cur =
+		    p->p_limit->pl_rlimit[i].rlim_max = RLIM_INFINITY;
+	p->p_limit->pl_rlimit[RLIMIT_NOFILE].rlim_cur =
+	    p->p_limit->pl_rlimit[RLIMIT_NOFILE].rlim_max = maxfiles;
+	p->p_limit->pl_rlimit[RLIMIT_NPROC].rlim_cur =
+	    p->p_limit->pl_rlimit[RLIMIT_NPROC].rlim_max = maxproc;
 	i = ptoa(cnt.v_free_count);
-	limit0.pl_rlimit[RLIMIT_RSS].rlim_max = i;
-	limit0.pl_rlimit[RLIMIT_MEMLOCK].rlim_max = i;
-	limit0.pl_rlimit[RLIMIT_MEMLOCK].rlim_cur = i / 3;
-	limit0.p_refcnt = 1;
+	p->p_limit->pl_rlimit[RLIMIT_RSS].rlim_max = i;
+	p->p_limit->pl_rlimit[RLIMIT_MEMLOCK].rlim_max = i;
+	p->p_limit->pl_rlimit[RLIMIT_MEMLOCK].rlim_cur = i / 3;
 	p->p_cpulimit = RLIM_INFINITY;
 
 	/* Allocate a prototype map so we have something to fork. */