forked from pool/glibc
49 lines
1.4 KiB
Diff
49 lines
1.4 KiB
Diff
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diff -rup c/nscd/nscd_gethst_r.c d/nscd/nscd_gethst_r.c
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--- c/nscd/nscd_gethst_r.c 2012-01-01 05:16:32.000000000 -0700
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+++ d/nscd/nscd_gethst_r.c 2012-03-28 10:45:51.546600822 -0600
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@@ -101,9 +101,27 @@ libc_freeres_fn (hst_map_free)
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uint32_t
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__nscd_get_nl_timestamp (void)
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{
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+ uint32_t retval;
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if (__nss_not_use_nscd_hosts != 0)
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return 0;
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+ int cnt = 0;
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+ /* __nscd_get_mapping can change hst_map_handle.mapped to NO_MAPPING.
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+ However, __nscd_get_mapping assumes the prior value was not NO_MAPPING.
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+ Thus we have to acquire the lock to prevent this thread from changing
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+ hst_map_handle.mapped to NO_MAPPING while another thread is inside
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+ __nscd_get_mapping. */
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+ while (__builtin_expect
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+ (atomic_compare_and_exchange_val_acq (&__hst_map_handle.lock,
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+ 1, 0) != 0, 0))
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+ {
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+ // XXX Best number of rounds?
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+ if (__builtin_expect (++cnt > 5, 0))
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+ return 0;
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+
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+ atomic_delay ();
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+ }
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+
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struct mapped_database *map = __hst_map_handle.mapped;
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if (map == NULL
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@@ -113,9 +131,14 @@ __nscd_get_nl_timestamp (void)
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map = __nscd_get_mapping (GETFDHST, "hosts", &__hst_map_handle.mapped);
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if (map == NO_MAPPING)
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- return 0;
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+ retval = 0;
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+ else
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+ retval = map->head->extra_data[NSCD_HST_IDX_CONF_TIMESTAMP];
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+
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+ /* Release the lock. */
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+ __hst_map_handle.lock = 0;
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- return map->head->extra_data[NSCD_HST_IDX_CONF_TIMESTAMP];
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+ return retval;
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}
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