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-rw-r--r--source/l/glibc/glibc-2.15.nscd-race-fix.diff47
1 files changed, 47 insertions, 0 deletions
diff --git a/source/l/glibc/glibc-2.15.nscd-race-fix.diff b/source/l/glibc/glibc-2.15.nscd-race-fix.diff
new file mode 100644
index 00000000..f1323570
--- /dev/null
+++ b/source/l/glibc/glibc-2.15.nscd-race-fix.diff
@@ -0,0 +1,47 @@
+--- c/nscd/nscd_gethst_r.c 2012-01-01 05:16:32.000000000 -0700
++++ c/nscd/nscd_gethst_r.c 2012-03-28 10:45:51.546600822 -0600
+@@ -101,9 +101,27 @@ libc_freeres_fn (hst_map_free)
+ uint32_t
+ __nscd_get_nl_timestamp (void)
+ {
++ uint32_t retval;
+ if (__nss_not_use_nscd_hosts != 0)
+ return 0;
+
++ int cnt = 0;
++ /* __nscd_get_mapping can change hst_map_handle.mapped to NO_MAPPING.
++ However, __nscd_get_mapping assumes the prior value was not NO_MAPPING.
++ Thus we have to acquire the lock to prevent this thread from changing
++ hst_map_handle.mapped to NO_MAPPING while another thread is inside
++ __nscd_get_mapping. */
++ while (__builtin_expect
++ (atomic_compare_and_exchange_val_acq (&__hst_map_handle.lock,
++ 1, 0) != 0, 0))
++ {
++ // XXX Best number of rounds?
++ if (__builtin_expect (++cnt > 5, 0))
++ return 0;
++
++ atomic_delay ();
++ }
++
+ struct mapped_database *map = __hst_map_handle.mapped;
+
+ if (map == NULL
+@@ -113,9 +131,14 @@ __nscd_get_nl_timestamp (void)
+ map = __nscd_get_mapping (GETFDHST, "hosts", &__hst_map_handle.mapped);
+
+ if (map == NO_MAPPING)
+- return 0;
++ retval = 0;
++ else
++ retval = map->head->extra_data[NSCD_HST_IDX_CONF_TIMESTAMP];
++
++ /* Release the lock. */
++ __hst_map_handle.lock = 0;
+
+- return map->head->extra_data[NSCD_HST_IDX_CONF_TIMESTAMP];
++ return retval;
+ }
+
+