[v2] malloc: Clean up __malloc_initialized

Message ID 20210618095351.1557461-1-siddhesh@sourceware.org
State New
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  • [v2] malloc: Clean up __malloc_initialized
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Commit Message

H.J. Lu via Libc-alpha June 18, 2021, 9:53 a.m.
It can be assumed that ptmalloc_init is always called in a
single-threaded context because pthread_create calls malloc before
spawning a thread.  As a result, a boolean value for
__malloc_initialized is sufficient to ensure that the function body is
executed only once.

Further, __malloc_initialized is mentioned in Versions when it is
actually an internal symbol.  Drop that reference and the macro
definition to __libc_malloc_initialized since it does not have an
external use.
---
Changes from v1:
- Retained attribute_hidden extern declaration.

 include/malloc.h |  6 ++----
 malloc/Versions  |  2 +-
 malloc/arena.c   | 16 +++++++++-------
 malloc/malloc.c  | 14 +++++++-------
 malloc/mcheck.c  |  2 +-
 5 files changed, 20 insertions(+), 20 deletions(-)

-- 
2.31.1

Comments

H.J. Lu via Libc-alpha June 22, 2021, 4:47 a.m. | #1
On 6/18/21 3:23 PM, Siddhesh Poyarekar via Libc-alpha wrote:
> It can be assumed that ptmalloc_init is always called in a

> single-threaded context because pthread_create calls malloc before

> spawning a thread.  As a result, a boolean value for

> __malloc_initialized is sufficient to ensure that the function body is

> executed only once.

> 

> Further, __malloc_initialized is mentioned in Versions when it is

> actually an internal symbol.  Drop that reference and the macro

> definition to __libc_malloc_initialized since it does not have an

> external use.

> ---

> Changes from v1:

> - Retained attribute_hidden extern declaration.



Florian what do you think?  I've made the change you requested.

Siddhesh
Siddhesh Poyarekar June 22, 2021, 12:46 p.m. | #2
On 6/18/21 3:23 PM, Siddhesh Poyarekar via Libc-alpha wrote:
> It can be assumed that ptmalloc_init is always called in a

> single-threaded context because pthread_create calls malloc before

> spawning a thread.  As a result, a boolean value for

> __malloc_initialized is sufficient to ensure that the function body is

> executed only once.

> 

> Further, __malloc_initialized is mentioned in Versions when it is

> actually an internal symbol.  Drop that reference and the macro

> definition to __libc_malloc_initialized since it does not have an

> external use.


Ahh no, this breaks mcheck initialization, which depends on the 
intermediate value to ensure it is initialized only once.  I'll figure 
out a way to work this into the hooks removal patchset since it 
simplifies the mcheck functionality a bit.

Siddhesh

Patch

diff --git a/include/malloc.h b/include/malloc.h
index b77761f74d..f8b7ebf250 100644
--- a/include/malloc.h
+++ b/include/malloc.h
@@ -4,12 +4,10 @@ 
 
 # ifndef _ISOMAC
 #  include <rtld-malloc.h>
+#  include <stdbool.h>
 
-/* In the GNU libc we rename the global variable
-   `__malloc_initialized' to `__libc_malloc_initialized'.  */
-#define __malloc_initialized __libc_malloc_initialized
 /* Nonzero if the malloc is already initialized.  */
-extern int __malloc_initialized attribute_hidden;
+extern bool __malloc_initialized attribute_hidden;
 
 struct malloc_state;
 typedef struct malloc_state *mstate;
diff --git a/malloc/Versions b/malloc/Versions
index 6693c46ee2..62e4698a08 100644
--- a/malloc/Versions
+++ b/malloc/Versions
@@ -9,7 +9,7 @@  libc {
     __libc_valloc;
     __malloc_initialize_hook; __free_hook; __malloc_hook; __realloc_hook;
     __memalign_hook; __after_morecore_hook;
-    __malloc_initialized; __default_morecore; __morecore;
+    __default_morecore; __morecore;
 
     # functions used in inline functions or macros
     _obstack_allocated_p; _obstack_begin; _obstack_begin_1;
diff --git a/malloc/arena.c b/malloc/arena.c
index 7eb110445e..bb14bc5ca9 100644
--- a/malloc/arena.c
+++ b/malloc/arena.c
@@ -97,7 +97,7 @@  static mstate free_list;
 __libc_lock_define_initialized (static, list_lock);
 
 /* Already initialized? */
-int __malloc_initialized = -1;
+bool __malloc_initialized;
 
 /**************************************************************************/
 
@@ -143,7 +143,7 @@  int __malloc_initialized = -1;
 void
 __malloc_fork_lock_parent (void)
 {
-  if (__malloc_initialized < 1)
+  if (!__malloc_initialized)
     return;
 
   /* We do not acquire free_list_lock here because we completely
@@ -163,7 +163,7 @@  __malloc_fork_lock_parent (void)
 void
 __malloc_fork_unlock_parent (void)
 {
-  if (__malloc_initialized < 1)
+  if (!__malloc_initialized)
     return;
 
   for (mstate ar_ptr = &main_arena;; )
@@ -179,7 +179,7 @@  __malloc_fork_unlock_parent (void)
 void
 __malloc_fork_unlock_child (void)
 {
-  if (__malloc_initialized < 1)
+  if (!__malloc_initialized)
     return;
 
   /* Push all arenas to the free list, except thread_arena, which is
@@ -287,13 +287,16 @@  extern struct dl_open_hook *_dl_open_hook;
 libc_hidden_proto (_dl_open_hook);
 #endif
 
+/* Malloc initialization.  We assume that the function is always called in a
+   single threaded context because pthread_create calls malloc before spawning
+   a thread.  */
 static void
 ptmalloc_init (void)
 {
-  if (__malloc_initialized >= 0)
+  if (__malloc_initialized)
     return;
 
-  __malloc_initialized = 0;
+  __malloc_initialized = true;
 
 #ifdef USE_MTAG
   if ((TUNABLE_GET_FULL (glibc, mem, tagging, int32_t, NULL) & 1) != 0)
@@ -410,7 +413,6 @@  ptmalloc_init (void)
   if (hook != NULL)
     (*hook)();
 #endif
-  __malloc_initialized = 1;
 }
 
 /* Managing heaps and arenas (for concurrent threads) */
diff --git a/malloc/malloc.c b/malloc/malloc.c
index 0e2e1747e0..0ba50a497b 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -3562,7 +3562,7 @@  libc_hidden_def (__libc_memalign)
 void *
 __libc_valloc (size_t bytes)
 {
-  if (__malloc_initialized < 0)
+  if (!__malloc_initialized)
     ptmalloc_init ();
 
   void *address = RETURN_ADDRESS (0);
@@ -3573,7 +3573,7 @@  __libc_valloc (size_t bytes)
 void *
 __libc_pvalloc (size_t bytes)
 {
-  if (__malloc_initialized < 0)
+  if (!__malloc_initialized)
     ptmalloc_init ();
 
   void *address = RETURN_ADDRESS (0);
@@ -5077,7 +5077,7 @@  __malloc_trim (size_t s)
 {
   int result = 0;
 
-  if (__malloc_initialized < 0)
+  if (!__malloc_initialized)
     ptmalloc_init ();
 
   mstate ar_ptr = &main_arena;
@@ -5212,7 +5212,7 @@  __libc_mallinfo2 (void)
   struct mallinfo2 m;
   mstate ar_ptr;
 
-  if (__malloc_initialized < 0)
+  if (!__malloc_initialized)
     ptmalloc_init ();
 
   memset (&m, 0, sizeof (m));
@@ -5263,7 +5263,7 @@  __malloc_stats (void)
   mstate ar_ptr;
   unsigned int in_use_b = mp_.mmapped_mem, system_b = in_use_b;
 
-  if (__malloc_initialized < 0)
+  if (!__malloc_initialized)
     ptmalloc_init ();
   _IO_flockfile (stderr);
   int old_flags2 = stderr->_flags2;
@@ -5432,7 +5432,7 @@  __libc_mallopt (int param_number, int value)
   mstate av = &main_arena;
   int res = 1;
 
-  if (__malloc_initialized < 0)
+  if (!__malloc_initialized)
     ptmalloc_init ();
   __libc_lock_lock (av->mutex);
 
@@ -5691,7 +5691,7 @@  __malloc_info (int options, FILE *fp)
 
 
 
-  if (__malloc_initialized < 0)
+  if (!__malloc_initialized)
     ptmalloc_init ();
 
   fputs ("<malloc version=\"1\">\n", fp);
diff --git a/malloc/mcheck.c b/malloc/mcheck.c
index 2a1fc645d4..acc6ad2e05 100644
--- a/malloc/mcheck.c
+++ b/malloc/mcheck.c
@@ -375,7 +375,7 @@  mcheck (void (*func) (enum mcheck_status))
   abortfunc = (func != NULL) ? func : &mabort;
 
   /* These hooks may not be safely inserted if malloc is already in use.  */
-  if (__malloc_initialized <= 0 && !mcheck_used)
+  if (!__malloc_initialized && !mcheck_used)
     {
       /* We call malloc() once here to ensure it is initialized.  */
       void *p = malloc (0);