PERFORCE change 85783 for review
John Baldwin
jhb at FreeBSD.org
Mon Oct 24 08:49:54 PDT 2005
http://perforce.freebsd.org/chv.cgi?CH=85783
Change 85783 by jhb at jhb_slimer on 2005/10/24 15:49:43
Don't panic if a spin lock is added that is not in the static order
list. Just warn about it instead.
Affected files ...
.. //depot/projects/smpng/sys/kern/subr_witness.c#140 edit
Differences ...
==== //depot/projects/smpng/sys/kern/subr_witness.c#140 (text+ko) ====
@@ -450,6 +450,12 @@
static int witness_cold = 1;
/*
+ * This global is set to 1 once the static lock orders have been enrolled
+ * so that a warning can be issued for any spin locks enrolled later.
+ */
+static int witness_spin_warn = 0;
+
+/*
* Global variables for book keeping.
*/
static int lock_cur_cnt;
@@ -500,6 +506,7 @@
w = w1;
}
}
+ witness_spin_warn = 1;
/* Iterate through all locks and add them to witness. */
mtx_lock(&all_mtx);
@@ -513,7 +520,7 @@
mtx_unlock(&all_mtx);
/* Mark the witness code as being ready for use. */
- atomic_store_rel_int(&witness_cold, 0);
+ witness_cold = 0;
mtx_lock(&Giant);
}
@@ -1403,13 +1410,15 @@
}
}
/*
- * This isn't quite right, as witness_cold is still 0 while we
- * enroll all the locks initialized before witness_initialize().
+ * We issue a warning for any spin locks not defined in the static
+ * order list as a way to discourage their use (folks should really
+ * be using non-spin mutexes most of the time). However, several
+ * 3rd part device drivers use spin locks because that is all they
+ * have available on Windows and Linux and they think that normal
+ * mutexes are insufficient.
*/
- if ((lock_class->lc_flags & LC_SPINLOCK) && !witness_cold) {
- mtx_unlock_spin(&w_mtx);
- panic("spin lock %s not in order list", description);
- }
+ if ((lock_class->lc_flags & LC_SPINLOCK) && witness_spin_warn)
+ printf("WITNESS: spin lock %s not in order list", description);
if ((w = witness_get()) == NULL)
return (NULL);
w->w_name = description;
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