kernel: simplify notify() adding common popnote() function

Handlin notes is common for all architectures
except how the note has to be pushed on the user
stack.

This change adds a popnote() function that returns
only the note string or nil if the process should
not be notified (no notes or user notes hold off).

Popnote() also handles common errors like notify
during note handling or missing note handler and
will suicide the process in that case.

1 files changed, 42 insertions, 0 deletions

diff --git a/sys/src/9/port/proc.c b/sys/src/9/port/proc.c
index 1fad45853..f0822f575 100644
--- a/sys/src/9/port/proc.c
+++ b/sys/src/9/port/proc.c
@@ -899,6 +899,48 @@ wakeup(Rendez *r)
 }
 
 /*
+ *  pop a note from the calling process or suicide if theres
+ *  no note handler or notify during note handling. 
+ *  Called from notify() with up->debug lock held.
+ */
+char*
+popnote(Ureg *u)
+{
+	assert(!canqlock(&up->debug));
+
+	up->notepending = 0;
+	if(up->nnote == 0)
+		return nil;
+	assert(up->nnote > 0);
+
+	/* hold off user notes during note handling */
+	if(up->notified && up->note[0].flag == NUser)
+		return nil;
+
+	memmove(&up->lastnote, &up->note[0], sizeof(Note));
+	if(--up->nnote)
+		memmove(&up->note[0], &up->note[1], up->nnote*sizeof(Note));
+
+	if(u != nil && strncmp(up->lastnote.msg, "sys:", 4) == 0){
+		int l = strlen(up->lastnote.msg);
+		assert(l < ERRMAX);
+		snprint(up->lastnote.msg+l, ERRMAX-l, " pc=%#p", u->pc);
+	}
+
+	if(up->notify == nil || up->notified){
+		qunlock(&up->debug);
+		if(up->lastnote.flag == NDebug){
+			up->fpstate &= ~FPillegal;
+			pprint("suicide: %s\n", up->lastnote.msg);
+		}
+		pexit(up->lastnote.msg, up->lastnote.flag!=NDebug);
+	}
+	up->notified = 1;
+
+	return up->lastnote.msg;
+}
+
+/*
  *  if waking a sleeping process, this routine must hold both
  *  p->rlock and r->lock.  However, it can't know them in
  *  the same order as wakeup causing a possible lock ordering