[PATCH v2] Set default stack size from program environment

[Siddhesh Poyarekar <siddhesh at redhat dot com>]

Hi,

This is take 2 to allow default stack size to be controlled
independently of process stack by using an environment variable so
that one need not change code for it.  Following my original
submission[1], Roland suggested that I break down the patch and post
them, with justifications for each of them.  The original intent of my
submission was to get the environment variable so that default thread
stack size can be controlled without having to change program code,
similar to features that AIX and Solaris provide.  The new API
functions were eye-candy to make the package complete, so I don't have
a separate justification for them other than that they 'complete the
implementation' so to speak.

As a result, this patch only implements the environment variable
support.  I will post the API functions patch separately on top of
this patch if this is accepted; I don't have any use for the API
functions alone.  Ditto for the manual patch.

The patch also includes a test case to verify the new feature.  No
regressions were reported in the testsuite due to this patch.

Siddhesh

[1] http://sourceware.org/ml/libc-alpha/2013-01/msg00572.html

ChangeLog:

	* csu/libc-start.c (__pthread_initialize_minimal): Change
	function arguments.
	* csu/libc-tls.c (__pthread_initialize_minimal): Likewise.

nptl/ChangeLog:

	* Makefile (tests): Add tst-pthread-stack-env.
	(tst-pthread-stack-env-ENV): Set environment for test.
	* nptl-init.c (set_default_stacksize): New function.
	(__pthread_initialize_minimal_internal): Accept ARGC, ARGV and
	ENVP.  Initialize __ENVIRON and set __DEFAULT_STACKSIZE.
        * tst-pthread-stack-env.c: New test case.


diff --git a/csu/libc-start.c b/csu/libc-start.c
index d4a135f..edd267c 100644
--- a/csu/libc-start.c
+++ b/csu/libc-start.c
@@ -31,7 +31,7 @@ extern int __libc_multiple_libcs;
 #include <tls.h>
 #ifndef SHARED
 # include <dl-osinfo.h>
-extern void __pthread_initialize_minimal (void);
+extern void __pthread_initialize_minimal (int, char **, char **);
 # ifndef THREAD_SET_STACK_GUARD
 /* Only exported for architectures that don't store the stack guard canary
    in thread local area.  */
@@ -174,7 +174,7 @@ LIBC_START_MAIN (int (*main) (int, char **, char ** MAIN_AUXVEC_DECL),
   /* Initialize the thread library at least a bit since the libgcc
      functions are using thread functions if these are available and
      we need to setup errno.  */
-  __pthread_initialize_minimal ();
+  __pthread_initialize_minimal (argc, argv, __environ);
 
   /* Set up the stack checker's canary.  */
   uintptr_t stack_chk_guard = _dl_setup_stack_chk_guard (_dl_random);
diff --git a/csu/libc-tls.c b/csu/libc-tls.c
index 90daaa6..f51a711 100644
--- a/csu/libc-tls.c
+++ b/csu/libc-tls.c
@@ -243,7 +243,7 @@ _dl_tls_setup (void)
    not used.  */
 void
 __attribute__ ((weak))
-__pthread_initialize_minimal (void)
+__pthread_initialize_minimal (int argc, char **argv, char **envp)
 {
   __libc_setup_tls (TLS_INIT_TCB_SIZE, TLS_INIT_TCB_ALIGN);
 }
diff --git a/nptl/Makefile b/nptl/Makefile
index 6af4b37..1a1ebec 100644
--- a/nptl/Makefile
+++ b/nptl/Makefile
@@ -251,7 +251,8 @@ tests = tst-typesizes \
 	tst-exec1 tst-exec2 tst-exec3 tst-exec4 \
 	tst-exit1 tst-exit2 tst-exit3 \
 	tst-stdio1 tst-stdio2 \
-	tst-stack1 tst-stack2 tst-stack3 tst-pthread-getattr \
+	tst-stack1 tst-stack2 tst-stack3 \
+	tst-pthread-getattr tst-pthread-stack-env \
 	tst-unload \
 	tst-dlsym1 \
 	tst-sysconf \
@@ -441,6 +442,8 @@ tst-cancel7-ARGS = --command "exec $(host-test-program-cmd)"
 tst-cancelx7-ARGS = $(tst-cancel7-ARGS)
 tst-umask1-ARGS = $(objpfx)tst-umask1.temp
 
+tst-pthread-stack-env-ENV = LIBC_PTHREAD_DEFAULT_STACKSIZE_NP=1048576
+
 $(objpfx)tst-atfork2: $(libdl) $(shared-thread-library)
 LDFLAGS-tst-atfork2 = -rdynamic
 tst-atfork2-ENV = MALLOC_TRACE=$(objpfx)tst-atfork2.mtrace
diff --git a/nptl/nptl-init.c b/nptl/nptl-init.c
index 19e6616..eb5fe77 100644
--- a/nptl/nptl-init.c
+++ b/nptl/nptl-init.c
@@ -276,8 +276,26 @@ extern void **__libc_dl_error_tsd (void) __attribute__ ((const));
 /* This can be set by the debugger before initialization is complete.  */
 static bool __nptl_initial_report_events __attribute_used__;
 
+static void
+set_default_stacksize (size_t stacksize)
+{
+  if (stacksize < PTHREAD_STACK_MIN)
+    stacksize = PTHREAD_STACK_MIN;
+
+  /* Make sure it meets the minimum size that allocate_stack
+     (allocatestack.c) will demand, which depends on the page size.  */
+  const uintptr_t pagesz = GLRO(dl_pagesize);
+  const size_t minstack = pagesz + __static_tls_size + MINIMAL_REST_STACK;
+
+  if (stacksize < minstack)
+    stacksize = minstack;
+
+  /* Round the resource limit up to page size.  */
+  stacksize = (stacksize + pagesz - 1) & -pagesz;
+  __default_stacksize = stacksize;
+}
 void
-__pthread_initialize_minimal_internal (void)
+__pthread_initialize_minimal_internal (int argc, char **argv, char **envp)
 {
 #ifndef SHARED
   /* Unlike in the dynamically linked case the dynamic linker has not
@@ -401,29 +419,41 @@ __pthread_initialize_minimal_internal (void)
 
   __static_tls_size = roundup (__static_tls_size, static_tls_align);
 
-  /* Determine the default allowed stack size.  This is the size used
-     in case the user does not specify one.  */
-  struct rlimit limit;
-  if (getrlimit (RLIMIT_STACK, &limit) != 0
-      || limit.rlim_cur == RLIM_INFINITY)
-    /* The system limit is not usable.  Use an architecture-specific
-       default.  */
-    limit.rlim_cur = ARCH_STACK_DEFAULT_SIZE;
-  else if (limit.rlim_cur < PTHREAD_STACK_MIN)
-    /* The system limit is unusably small.
-       Use the minimal size acceptable.  */
-    limit.rlim_cur = PTHREAD_STACK_MIN;
+  /* Initialize the environment.  libc.so gets initialized after us due to a
+     circular dependency and hence __environ is not available otherwise.  */
+    __environ = envp;
 
-  /* Make sure it meets the minimum size that allocate_stack
-     (allocatestack.c) will demand, which depends on the page size.  */
-  const uintptr_t pagesz = GLRO(dl_pagesize);
-  const size_t minstack = pagesz + __static_tls_size + MINIMAL_REST_STACK;
-  if (limit.rlim_cur < minstack)
-    limit.rlim_cur = minstack;
+#ifndef SHARED
+    __libc_init_secure ();
+#endif
 
-  /* Round the resource limit up to page size.  */
-  limit.rlim_cur = (limit.rlim_cur + pagesz - 1) & -pagesz;
-  __default_stacksize = limit.rlim_cur;
+  size_t stacksize = 0;
+  char *envval = __libc_secure_getenv ("LIBC_PTHREAD_DEFAULT_STACKSIZE_NP");
+
+  if (__glibc_unlikely (envval != NULL && envval[0] != '\0'))
+    {
+      char *env_conv = envval;
+      size_t ret = strtoul (envval, &env_conv, 0);
+
+      if (*env_conv == '\0')
+	stacksize = ret;
+    }
+
+  if (stacksize == 0)
+    {
+      /* Determine the default allowed stack size.  This is the size used
+	 in case the user does not specify one.  */
+      struct rlimit limit;
+      if (getrlimit (RLIMIT_STACK, &limit) != 0
+	  || limit.rlim_cur == RLIM_INFINITY)
+	/* The system limit is not usable.  Use an architecture-specific
+	   default.  */
+	stacksize = ARCH_STACK_DEFAULT_SIZE;
+      else
+	stacksize = limit.rlim_cur;
+    }
+
+  set_default_stacksize (stacksize);
 
 #ifdef SHARED
   /* Transfer the old value from the dynamic linker's internal location.  */
diff --git a/nptl/tst-pthread-stack-env.c b/nptl/tst-pthread-stack-env.c
new file mode 100644
index 0000000..0c7273e
--- /dev/null
+++ b/nptl/tst-pthread-stack-env.c
@@ -0,0 +1,72 @@
+/* Verify that pthreads uses the default thread stack size set with the
+   LIBC_PTHREAD_DEFAULT_STACKSIZE_NP environment variable.
+   Copyright (C) 2013 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <pthread.h>
+#include <stdio.h>
+#include <string.h>
+
+#define STACKSIZE 1024 * 1024L
+
+void *
+thr (void *u)
+{
+  size_t stacksize, guardsize;
+  pthread_attr_t attr;
+  pthread_getattr_np (pthread_self (), &attr);
+
+  pthread_attr_getstacksize (&attr, &stacksize);
+  pthread_attr_getguardsize (&attr, &guardsize);
+
+  /* FIXME once guardsize is excluded from stacksize.  */
+  if (stacksize - guardsize != STACKSIZE)
+    {
+      printf ("Stack size is %zu, should be %zu\n", stacksize - guardsize,
+	      STACKSIZE);
+      return (void *) 1;
+    }
+
+  return NULL;
+}
+
+int
+do_test (int argc, char **argv)
+{
+  pthread_t t;
+  void *thr_ret;
+  int ret;
+
+  if ((ret = pthread_create (&t, NULL, thr, NULL)) != 0)
+    {
+      printf ("thread create failed: %s\n", strerror (ret));
+      return 1;
+    }
+
+  if ((ret = pthread_join (t, &thr_ret)) != 0)
+    {
+      printf ("join failed: %s\n", strerror (ret));
+      return 1;
+    }
+
+  if (thr_ret != NULL && thr_ret != PTHREAD_CANCELED)
+    return 1;
+
+  return 0;
+}
+
+#include "../test-skeleton.c"