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x509v3/v3_purp.c: refine lock-free check in x509v3_cache_extensions.

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Reviewed-by: Kurt Roeckx <kurt@roeckx.be>
(Merged from https://github.com/openssl/openssl/pull/6996)
This commit is contained in:
Andy Polyakov 2018-08-17 12:30:36 +02:00
parent a88e328c3a
commit 7d38ca3f8b
1 changed files with 10 additions and 6 deletions

16
crypto/x509v3/v3_purp.c

@ -354,9 +354,11 @@ static void x509v3_cache_extensions(X509 *x)
X509_EXTENSION *ex;
int i;
#ifdef tsan_ld_acq
/* fast lock-free check, see end of the function for details. */
if (tsan_load((TSAN_QUALIFIER int *)&x->ex_cached))
if (tsan_ld_acq((TSAN_QUALIFIER int *)&x->ex_cached))
return;
#endif
CRYPTO_THREAD_write_lock(x->lock);
if (x->ex_flags & EXFLAG_SET) {
@ -498,13 +500,15 @@ static void x509v3_cache_extensions(X509 *x)
}
x509_init_sig_info(x);
x->ex_flags |= EXFLAG_SET;
CRYPTO_THREAD_unlock(x->lock);
#ifdef tsan_st_rel
tsan_st_rel((TSAN_QUALIFIER int *)&x->ex_cached, 1);
/*
* It has to be placed after memory barrier, which is implied by unlock.
* Worst thing that can happen is that another thread proceeds to lock
* and checks x->ex_flags & EXFLAGS_SET. See beginning of the function.
* Above store triggers fast lock-free check in the beginning of the
* function. But one has to ensure that the structure is "stable", i.e.
* all stores are visible on all processors. Hence the release fence.
*/
tsan_store((TSAN_QUALIFIER int *)&x->ex_cached, 1);
#endif
CRYPTO_THREAD_unlock(x->lock);
}
/*-