OS-4112 stack overflow from promisc callbacks
Reviewed by: Jerry Jelinek <jerry.jelinek@joyent.com>

@@ -21,39 +21,41 @@
 
 /*
  * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
  */
-
 /*
- * FILE NOTICE BEGIN
- *
- * This file should not be modified.  If you wish to modify it or have it
- * modified, please contact Sun Microsystems at <LFI149367@-sun-.-com->
- * (without anti-spam dashes)
- *
- * FILE NOTICE END
+ * Copyright 2015, Joyent, Inc.
  */
 
-#pragma ident   "%Z%%M% %I%     %E% SMI"
-
 #include <sys/cpuvar.h>
 #include <sys/stack.h>
 #include <vm/seg_kp.h>
 #include <sys/proc.h>
 #include <sys/pset.h>
 #include <sys/sysmacros.h>
 
 /*
+ * Use a slightly larger thread stack size for interrupt threads rather than the
+ * default. This is useful for cases where the networking stack may do an rx and
+ * a tx in the context of a single interrupt and when combined with various
+ * promisc hooks that need memory, can cause us to get dangerously close to the
+ * edge of the traditional stack sizes. This is only a few pages more than a
+ * traditional stack and given that we don't have that many interrupt threads,
+ * the memory costs end up being more than worthwhile.
+ */
+#define LL_INTR_STKSZ   (32 * 1024)
+
+/*
  * Create and initialize an interrupt thread.
  */
 static void
 thread_create_intr(cpu_t *cp)
 {
         kthread_t *tp;
 
-        tp = thread_create(NULL, 0,
+        tp = thread_create(NULL, LL_INTR_STKSZ,
             (void (*)())thread_create_intr, NULL, 0, &p0, TS_ONPROC, 0);
 
         /*
          * Set the thread in the TS_FREE state.  The state will change
          * to TS_ONPROC only while the interrupt is active.  Think of these

@@ -95,13 +97,16 @@
         tp->t_link = cp->cpu_intr_thread;
         cp->cpu_intr_thread = tp;
 }
 
 /*
- * Allocate a given number of interrupt threads for a given CPU.
- * These threads will get freed by cpu_destroy_bound_threads()
- * when CPU gets unconfigured.
+ * Allocate a given number of interrupt threads for a given CPU.  These threads
+ * will get freed by cpu_destroy_bound_threads() when CPU gets unconfigured.
+ *
+ * Note, high level interrupts are always serviced using cpu_intr_stack and are
+ * not allowed to block. Low level interrupts or soft-interrupts use the
+ * kthread_t's that we create through the calls to thread_create_intr().
  */
 void
 cpu_intr_alloc(cpu_t *cp, int n)
 {
         int i;