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, 4 insertions, 4 deletions

diff --git a/sys/kern/subr_trap.c b/sys/kern/subr_trap.c
index 2390087..a556d0e 100644
--- a/sys/kern/subr_trap.c
+++ b/sys/kern/subr_trap.c
@@ -143,7 +143,7 @@ ast(struct trapframe *framep)
 	struct proc *p;
 	struct kse *ke;
 	struct ksegrp *kg;
-	struct rlimit *rlim;
+	struct rlimit rlim;
 	u_int prticks, sticks;
 	int sflag;
 	int flags;
@@ -223,13 +223,13 @@ ast(struct trapframe *framep)
 	}
 	if (sflag & PS_XCPU) {
 		PROC_LOCK(p);
-		rlim = &p->p_rlimit[RLIMIT_CPU];
+		lim_rlimit(p, RLIMIT_CPU, &rlim);
 		mtx_lock_spin(&sched_lock);
-		if (p->p_runtime.sec >= rlim->rlim_max) {
+		if (p->p_runtime.sec >= rlim.rlim_max) {
 			mtx_unlock_spin(&sched_lock);
 			killproc(p, "exceeded maximum CPU limit");
 		} else {
-			if (p->p_cpulimit < rlim->rlim_max)
+			if (p->p_cpulimit < rlim.rlim_max)
 				p->p_cpulimit += 5;
 			mtx_unlock_spin(&sched_lock);
 			psignal(p, SIGXCPU);