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Cygwin: pthreads: iterate over key destructors per POSIX 

POSIX requires that key destructors are called in a loop
for each key with a non-NULL value until all values are
NULL, or until all destructors for non-NULL values
have been called at least PTHREAD_DESTRUCTOR_ITERATIONS
(per POSIX: 4) times.

Cygwinonly called all destructors with non-NULL values
exactly once.  This patch fixes Cygwin to follow POSIX.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
This commit is contained in:
Corinna Vinschen 2020-08-29 21:08:31 +02:00
parent 1cab623527
commit b9ad0fbf28
3 changed files with 24 additions and 7 deletions
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7
winsup/cygwin/include/limits.h
View File

@ -225,13 +225,8 @@ details. */
/* Maximum number of attempts made to destroy a thread's thread-specific
data values on thread exit. */
/* FIXME: I really don't understand this value. Why should multiple
attempts be necessary to destroy thread-specific data?!? Anyway, the
current value here is 1, taken originally from our pthread.h file,
where it was mistakenly defined first. Unfortunately this value is
lower than the POSIX defined minimum value, which is 4. */
#undef PTHREAD_DESTRUCTOR_ITERATIONS
#define PTHREAD_DESTRUCTOR_ITERATIONS 1
#define PTHREAD_DESTRUCTOR_ITERATIONS 4
/* Maximum number of data keys that can be created by a process. */
/* Tls has 1088 items - and we don't want to use them all :] */

4
winsup/cygwin/thread.cc
View File

@ -1713,6 +1713,8 @@ pthread_key::_fixup_after_fork ()
set (fork_buf);
}
bool pthread_key::iterate_dtors_once_more;
void
pthread_key::run_destructor ()
{
@ -1723,6 +1725,8 @@ pthread_key::run_destructor ()
{
set (NULL);
destructor (oldValue);
if (get ())
iterate_dtors_once_more = true;
}
}
}

20
winsup/cygwin/thread.h
View File

@ -197,6 +197,7 @@ protected:
class pthread_key: public verifyable_object
{
DWORD tls_index;
static bool iterate_dtors_once_more;
public:
static bool is_good_object (pthread_key_t const *);
@ -218,7 +219,24 @@ public:
static void run_all_destructors ()
{
keys.for_each (&pthread_key::run_destructor);
/* POSIX requires at least four iterations of running destructors:
If, after all the destructors have been called for all non-NULL
values with associated destructors, there are still some non-NULL
values with associated destructors, then the process is repeated.
If, after at least {PTHREAD_DESTRUCTOR_ITERATIONS} iterations of
destructor calls for outstanding non-NULL values, there are still
some non-NULL values with associated destructors, implementations
may stop calling destructors, or they may continue calling
destructors until no non-NULL values with associated destructors
exist, even though this might result in an infinite loop. */
for (int i = 0; i < PTHREAD_DESTRUCTOR_ITERATIONS; ++i)
{
iterate_dtors_once_more = false;
keys.for_each (&pthread_key::run_destructor);
if (!iterate_dtors_once_more)
break;
}
}
/* List support calls */