kernel: avoid palloc lock during mmurelease()

Previously, mmurelease() was always called with
palloc spinlock held.

This is unneccesary for some mmurelease()
implementations as they wont release pages
to the palloc pool.

This change removes pagechainhead() and
pagechaindone() and replaces them with just
freepages() call, which aquires the palloc
lock internally as needed.

freepages() avoids holding the palloc lock
while walking the linked list of pages,
avoding some lock contention.

1 files changed, 5 insertions, 15 deletions

diff --git a/sys/src/9/port/proc.c b/sys/src/9/port/proc.c
index a51232d44..567ab0756 100644
--- a/sys/src/9/port/proc.c
+++ b/sys/src/9/port/proc.c
@@ -81,27 +81,21 @@ schedinit(void)		/* never returns */
 		case Moribund:
 			up->state = Dead;
 			edfstop(up);
-			if(up->edf != nil)
+			if(up->edf != nil){
 				free(up->edf);
-			up->edf = nil;
+				up->edf = nil;
+			}
 
-			/*
-			 * Holding locks from pexit:
-			 * 	procalloc
-			 *	palloc
-			 */
 			mmurelease(up);
-			unlock(&palloc);
 
-			updatecpu(up);
+			lock(&procalloc);
 			up->mach = nil;
-
 			up->qnext = procalloc.free;
 			procalloc.free = up;
-
 			/* proc is free now, make sure unlock() wont touch it */
 			up = procalloc.Lock.p = nil;
 			unlock(&procalloc);
+
 			sched();
 		}
 		coherence();
@@ -1223,10 +1217,6 @@ pexit(char *exitstr, int freemem)
 	}
 	qunlock(&up->seglock);
 
-	/* Sched must not loop for these locks */
-	lock(&procalloc);
-	lock(&palloc);
-
 	edfstop(up);
 	up->state = Moribund;
 	sched();