From: Matthew Dillon <dillon@dragonflybsd.org>
Date: Mon, 20 Jun 2005 07:40:30 +0000 (+0000)
Subject: Tokens are recursive in the context of the same thread.  This also means
X-Git-Tag: v2.0.1~6858
X-Git-Url: https://gitweb.dragonflybsd.org/dragonfly.git/commitdiff_plain/897eef074bbb7aa718e9c0eac3d721c4b5e2c3a2

Tokens are recursive in the context of the same thread.  This also means
that fast interrupts such as IPIs cannot safely use any token function.
Assert this requirement in the implementation.

Add miscellanious other assertions to enforce correct operation.

Remove the 'no giveaway' warning.  This warning was being used to determine
where recursive tokens were being used.  It turns out that they are used
in the mountlist scan code (which has historically been rather buggy).  Now
that we know where they are used and we fixed the recursion release bug in
a prior commit, this printf() can be removed.
---

diff --git a/sys/kern/lwkt_token.c b/sys/kern/lwkt_token.c
index 5c46ed14d9..55f8578253 100644
--- a/sys/kern/lwkt_token.c
+++ b/sys/kern/lwkt_token.c
@@ -31,7 +31,7 @@
  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  * 
- * $DragonFly: src/sys/kern/lwkt_token.c,v 1.16 2005/06/19 21:50:47 dillon Exp $
+ * $DragonFly: src/sys/kern/lwkt_token.c,v 1.17 2005/06/20 07:40:30 dillon Exp $
  */
 
 #ifdef _KERNEL
@@ -132,6 +132,7 @@ lwkt_chktokens(thread_t td)
     __uint32_t magic;
     int r = 1;
 
+    KKASSERT(gd->gd_curthread->td_pri >= TDPRI_CRIT);
     for (refs = td->td_toks; refs; refs = refs->tr_next) {
 	tok = refs->tr_tok;
 	if ((dgd = tok->t_cpu) != gd) {
@@ -236,6 +237,7 @@ _lwkt_gettokref(lwkt_tokref_t ref)
 
     gd = mycpu;			/* our cpu */
     KKASSERT(ref->tr_magic == LWKT_TOKREF_MAGIC1);
+    KKASSERT(gd->gd_intr_nesting_level == 0);
     td = gd->gd_curthread;	/* our thread */
 
     /*
@@ -319,6 +321,7 @@ _lwkt_trytokref(lwkt_tokref_t ref)
 
     gd = mycpu;			/* our cpu */
     KKASSERT(ref->tr_magic == LWKT_TOKREF_MAGIC1);
+    KKASSERT(gd->gd_intr_nesting_level == 0);
     td = gd->gd_curthread;	/* our thread */
 
     /*
@@ -429,7 +432,9 @@ lwkt_reltoken(lwkt_tokref *_ref)
     tok = ref->tr_tok;
     gd = mycpu;
     td = gd->gd_curthread;
+
     KKASSERT(tok->t_cpu == gd);
+    KKASSERT(gd->gd_intr_nesting_level == 0);
 
     /*
      * We can only give away the token if we aren't holding it recursively.
@@ -448,10 +453,6 @@ lwkt_reltoken(lwkt_tokref *_ref)
 	if (scan->tr_tok == tok)
 	    giveaway = 0;
     }
-    if (giveaway == 0) {
-	printf("Warning: no giveaway lwkt_reltoken caller %p\n",
-		((void **)&_ref)[-1]);
-    }
 
     /*
      * Give the token away (if we can) before removing the interlock.  Once
@@ -459,6 +460,7 @@ lwkt_reltoken(lwkt_tokref *_ref)
      */
     if (giveaway)
 	tok->t_cpu = tok->t_reqcpu;	
+    KKASSERT(*pref == ref);
     *pref = ref->tr_next;
 
     /*
@@ -557,6 +559,7 @@ lwkt_drain_token_requests(void)
     globaldata_t gd = mycpu;
     lwkt_tokref_t ref;
 
+    KKASSERT(gd->gd_curthread->td_pri >= TDPRI_CRIT);
     while ((ref = gd->gd_tokreqbase) != NULL) {
 	gd->gd_tokreqbase = ref->tr_gdreqnext;
 	KKASSERT(ref->tr_magic == LWKT_TOKREF_MAGIC2);