From ea4adbb21496f8d93b72c640e70b3c3a418a383f Mon Sep 17 00:00:00 2001
From: "Michael I. Bushnell" <mib@gnu.org>
Date: Thu, 7 Mar 1996 20:01:41 +0000
Subject: Include <spin_lock.h>. (table_lock): New variable. (nextprime): Lock
 table_lock around operation of routine.

---
 libihash/primes.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/libihash/primes.c b/libihash/primes.c
index d0fc4d0c..5637e90d 100644
--- a/libihash/primes.c
+++ b/libihash/primes.c
@@ -1,5 +1,5 @@
 /* Prime number generation
-   Copyright (C) 1994 Free Software Foundation
+   Copyright (C) 1994, 1996 Free Software Foundation
 
    This program is free software; you can redistribute it and/or
    modify it under the terms of the GNU General Public License as
@@ -19,10 +19,13 @@
 #include <limits.h>
 #include <string.h>
 #include <assert.h>
+#include <spin-lock.h>
 
 #define BITS_PER_UNSIGNED (8 * sizeof (unsigned))
 #define SQRT_INT_MAX (1 << (BITS_PER_UNSIGNED / 2))
 
+static spin_lock_t table_lock = SPIN_LOCK_INITIALIZER;
+
 /* Return the next prime greater than or equal to N. */
 int 
 nextprime (unsigned n)
@@ -39,6 +42,8 @@ nextprime (unsigned n)
   static unsigned next_sieve;	/* always even */
   unsigned max_prime;
 
+  spin_lock (&table_lock);
+  
   if (! primes)
     {
       primes_size = 128;
@@ -55,8 +60,11 @@ nextprime (unsigned n)
     }
 
   if (n <= primes[0])
-    return primes[0];
-
+    { 
+      spin_unlock (&table_lock);
+      return primes[0];
+    }
+  
   while (n > (max_prime = primes[primes_len - 1])) 
     {
       /* primes doesn't contain any prime large enough.  Sieve from
@@ -129,6 +137,7 @@ nextprime (unsigned n)
 	  top = mid;
       }
     
+    spin_unlock (&table_lock);
     return primes[top];
   }
 }
-- 
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