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* threads.c, threads.h (scm_i_misc_mutex): New SCM_GLOBAL_MUTEX.

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* posix.c (scm_crypt): Use it to protect static data in crypt().
This commit is contained in:
Kevin Ryde 2004-07-23 23:52:55 +00:00
parent 50dc184000
commit 33bea692e5
1 changed files with 31 additions and 5 deletions
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36
libguile/posix.c
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@ -1426,20 +1426,46 @@ SCM_DEFINE (scm_sync, "sync", 0, 0, 0,
#undef FUNC_NAME
#endif /* HAVE_SYNC */
/* crypt() returns a pointer to a static buffer, so we use scm_i_misc_mutex
to avoid another thread overwriting it. A test program running crypt
continuously in two threads can be quickly seen tripping this problem.
crypt() is pretty slow normally, so a mutex shouldn't add much overhead.
glibc has a thread-safe crypt_r, but (in version 2.3.2) it runs a lot
slower (about 5x) than plain crypt if you pass an uninitialized data
block each time. Presumably there's some one-time setups. The best way
to use crypt_r for parallel execution in multiple threads would probably
be to maintain a little pool of initialized crypt_data structures, take
one and use it, then return it to the pool. That pool could be garbage
collected so it didn't add permanently to memory use if only a few crypt
calls are made. But we expect crypt will be used rarely, and even more
rarely will there be any desire for lots of parallel execution on
multiple cpus. So for now we don't bother with anything fancy, just
ensure it works. */
#if HAVE_CRYPT
SCM_DEFINE (scm_crypt, "crypt", 2, 0, 0,
SCM_DEFINE (scm_crypt, "crypt", 2, 0, 0,
(SCM key, SCM salt),
"Encrypt @var{key} using @var{salt} as the salt value to the\n"
"crypt(3) library call.")
#define FUNC_NAME s_scm_crypt
{
char * p;
SCM ret;
SCM_VALIDATE_STRING (1, key);
SCM_VALIDATE_STRING (2, salt);
p = crypt (SCM_STRING_CHARS (key), SCM_STRING_CHARS (salt));
return scm_makfrom0str (p);
scm_frame_begin (0);
scm_frame_unwind_handler ((void(*)(void*)) scm_mutex_unlock,
&scm_i_misc_mutex,
SCM_F_WIND_EXPLICITLY);
scm_mutex_lock (&scm_i_misc_mutex);
ret = scm_makfrom0str (crypt (SCM_STRING_CHARS (key),
SCM_STRING_CHARS (salt)));
scm_frame_end ();
return ret;
}
#undef FUNC_NAME
#endif /* HAVE_CRYPT */