perl.h: Add capability for many-reader ENV mutex locking

There are several places where there could be a problem in the
environment were changed by another thread when a function is executing,
but otherwise if another thread were reading the environment at the same
time, there isn't a problem.  This adds mutex for that situation.
Future commits will take advantage of it.

diff --git a/perl.h b/perl.h
index 76b6e72..9243ca8 100644 (file)
--- a/perl.h
+++ b/perl.h
@@ -7003,19 +7003,19 @@ cannot have changed since the precalculation.
 #endif /* !USE_LOCALE_NUMERIC */
 
 #ifdef USE_ITHREADS
-   /* On some platforms it would be safe to use a read/write mutex with many
-    * readers possible at the same time.  On other platforms, notably IBM ones,
-    * subsequent getenv calls destroy earlier ones.  Those platforms would not
-    * be able to handle simultaneous getenv calls */
-#  define ENV_LOCK            MUTEX_LOCK(&PL_env_mutex)
-#  define ENV_UNLOCK          MUTEX_UNLOCK(&PL_env_mutex)
-#  define ENV_INIT            MUTEX_INIT(&PL_env_mutex);
-#  define ENV_TERM            MUTEX_DESTROY(&PL_env_mutex);
+#  define ENV_LOCK            PERL_WRITE_LOCK(&PL_env_mutex)
+#  define ENV_UNLOCK          PERL_WRITE_UNLOCK(&PL_env_mutex)
+#  define ENV_READ_LOCK       PERL_READ_LOCK(&PL_env_mutex)
+#  define ENV_READ_UNLOCK     PERL_READ_UNLOCK(&PL_env_mutex)
+#  define ENV_INIT            PERL_RW_MUTEX_INIT(&PL_env_mutex)
+#  define ENV_TERM            PERL_RW_MUTEX_DESTROY(&PL_env_mutex)
 #else
-#  define ENV_LOCK       NOOP
-#  define ENV_UNLOCK     NOOP
-#  define ENV_INIT       NOOP
-#  define ENV_TERM       NOOP
+#  define ENV_LOCK        NOOP
+#  define ENV_UNLOCK      NOOP
+#  define ENV_READ_LOCK   NOOP
+#  define ENV_READ_UNLOCK NOOP
+#  define ENV_INIT        NOOP
+#  define ENV_TERM        NOOP
 #endif
 
 #ifndef PERL_NO_INLINE_FUNCTIONS

diff --git a/perlvars.h b/perlvars.h
index 1bbe5e3..3bfd46f 100644 (file)
--- a/perlvars.h
+++ b/perlvars.h
@@ -104,7 +104,7 @@ PERLVARI(G, mmap_page_size, IV, 0)
 
 #if defined(USE_ITHREADS)
 PERLVAR(G, hints_mutex, perl_mutex)    /* Mutex for refcounted he refcounting */
-PERLVAR(G, env_mutex, perl_mutex)      /* Mutex for accessing ENV */
+PERLVAR(G, env_mutex, perl_RnW1_mutex_t)      /* Mutex for accessing ENV */
 PERLVAR(G, locale_mutex, perl_mutex)   /* Mutex related to locale handling */
 #  ifndef USE_THREAD_SAFE_LOCALE
 PERLVAR(G, lc_numeric_mutex, perl_mutex)   /* Mutex for switching LC_NUMERIC */