From patchwork Wed Jul 12 15:56:31 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Paul Pluzhnikov X-Patchwork-Id: 21561 Received: (qmail 102149 invoked by alias); 12 Jul 2017 15:57:08 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Delivered-To: mailing list libc-alpha@sourceware.org Received: (qmail 101151 invoked by uid 89); 12 Jul 2017 15:57:07 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-24.9 required=5.0 tests=AWL, BAYES_00, GIT_PATCH_0, GIT_PATCH_1, GIT_PATCH_2, GIT_PATCH_3, RCVD_IN_DNSWL_NONE, RP_MATCHES_RCVD, SPF_PASS, URIBL_RED autolearn=ham version=3.3.2 spammy= X-HELO: mail-ua0-f182.google.com X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=U9R1GuT2b9/+ccN3SEJtJQ4G4uuY3IC+yiyY4alZ1S0=; b=cP8v120S7/7fyC2CM2BHAZKGXXuAXIOKTyhq9yQCgRz+wRn9aThq5Wh/0qtmxDEwdC QU8sUMl1nBM4P/B4St11dayW7zvwrp5CGkGf0sEgIDLV0pQgvporoPCVbPSVrt0VvRn+ ER/WYy4Yi0crUdGn0QLTMnEHJjlVMNywQZQRpqoej6XeKx+zI8Jd5IfykGOuZmi9kotd SfhskL3sS0sX82P5WMlUfswUjSP87NnXQJzx17r8ihwwkdO9WwIo6xuBWnnr35d1myrB fkq9Vz5Xb6Kh/0OP8G4M/3l9l/pZbUm1JOft50LGdM21cQ9lgVgzSVlGI4lNfnho1rno 09vw== X-Gm-Message-State: AIVw113xLK8Lnvwbt4IEi+Rvky5Uzgr+i9Ka3CeXPYaVRsFLlQzQnXUL HCy+jnP24oCLw9FJmPJ1qFMdMfBmriLy X-Received: by 10.176.79.146 with SMTP id m18mr3642584uah.83.1499875022159; Wed, 12 Jul 2017 08:57:02 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: References: From: Paul Pluzhnikov Date: Wed, 12 Jul 2017 08:56:31 -0700 Message-ID: Subject: Re: [patch] Fix for bz14333 -- race between atexit() and exit() To: Joseph Myers Cc: GLIBC Devel , Ricky Zhou On Tue, Jul 11, 2017 at 12:01 PM, Joseph Myers wrote: > A patch fixing a bug should also include the tests for that bug. Revised patch attached. Thanks. 2017-07-12 Paul Pluzhnikov Ricky Zhou Anoop V Chakkalakkal [BZ #14333] * stdlib/cxa_atexit.c (__internal_atexit): Use __exit_funcs_lock. (__new_exitfn): Fail registration when we finished at_exit processing. * stdlib/on_exit.c (__on_exit): Likewise. * stdlib/exit.c (__exit_funcs_done): New variable. (__run_exit_handlers): Use __exit_funcs_lock. * stdlib/exit.h (__exit_funcs_lock, __exit_funcs_done): New declarations. * stdlib/Makefile (test-atexit-race, test-quick_at_exit-race) (test-__cxa_atexit-race): New tests. * stdlib/test-atexit-race-common.c: New. * stdlib/test-atexit-race.c: New. * stdlib/test-at_quick_exit-race.c: New. * stdlib/test-__cxa_atexit-race.c: New. diff --git a/stdlib/Makefile b/stdlib/Makefile index 0314d5926b..7731b53cc8 100644 --- a/stdlib/Makefile +++ b/stdlib/Makefile @@ -80,7 +80,8 @@ tests := tst-strtol tst-strtod testmb testrand testsort testdiv \ tst-strtol-locale tst-strtod-nan-locale tst-strfmon_l \ tst-quick_exit tst-thread-quick_exit tst-width \ tst-width-stdint tst-strfrom tst-strfrom-locale \ - tst-getrandom + tst-getrandom test-atexit-race test-at_quick_exit-race \ + test-__cxa_atexit-race tests-internal := tst-strtod1i tst-strtod3 tst-strtod4 tst-strtod5i \ tst-tls-atexit tst-tls-atexit-nodelete tests-static := tst-secure-getenv @@ -89,6 +90,10 @@ ifeq ($(build-hardcoded-path-in-tests),yes) tests += tst-empty-env endif +LDLIBS-test-atexit-race = $(shared-thread-library) +LDLIBS-test-at_quick_exit-race = $(shared-thread-library) +LDLIBS-test-__cxa_atexit-race = $(shared-thread-library) + ifeq ($(have-cxx-thread_local),yes) CFLAGS-tst-quick_exit.o = -std=c++11 LDLIBS-tst-quick_exit = -lstdc++ diff --git a/stdlib/cxa_atexit.c b/stdlib/cxa_atexit.c index ce5d9f22b4..5db0b33060 100644 --- a/stdlib/cxa_atexit.c +++ b/stdlib/cxa_atexit.c @@ -26,16 +26,25 @@ #undef __cxa_atexit +/* We change global data, so we need locking. */ +__libc_lock_define_initialized (, __exit_funcs_lock) + int attribute_hidden __internal_atexit (void (*func) (void *), void *arg, void *d, struct exit_function_list **listp) { - struct exit_function *new = __new_exitfn (listp); + struct exit_function *new; + + __libc_lock_lock (__exit_funcs_lock); + new = __new_exitfn (listp); if (new == NULL) - return -1; + { + __libc_lock_unlock (__exit_funcs_lock); + return -1; + } #ifdef PTR_MANGLE PTR_MANGLE (func); @@ -45,6 +54,7 @@ __internal_atexit (void (*func) (void *), void *arg, void *d, new->func.cxa.dso_handle = d; atomic_write_barrier (); new->flavor = ef_cxa; + __libc_lock_unlock (__exit_funcs_lock); return 0; } @@ -60,10 +70,6 @@ __cxa_atexit (void (*func) (void *), void *arg, void *d) libc_hidden_def (__cxa_atexit) -/* We change global data, so we need locking. */ -__libc_lock_define_initialized (static, lock) - - static struct exit_function_list initial; struct exit_function_list *__exit_funcs = &initial; uint64_t __new_exitfn_called; @@ -76,7 +82,10 @@ __new_exitfn (struct exit_function_list **listp) struct exit_function *r = NULL; size_t i = 0; - __libc_lock_lock (lock); + if (__exit_funcs_done == 1) + /* exit code finished processing all handlers + so fail this registration */ + return NULL; for (l = *listp; l != NULL; p = l, l = l->next) { @@ -127,7 +136,5 @@ __new_exitfn (struct exit_function_list **listp) ++__new_exitfn_called; } - __libc_lock_unlock (lock); - return r; } diff --git a/stdlib/exit.c b/stdlib/exit.c index c0b6d666c7..dfc4474891 100644 --- a/stdlib/exit.c +++ b/stdlib/exit.c @@ -19,11 +19,14 @@ #include #include #include +#include #include "exit.h" #include "set-hooks.h" DEFINE_HOOK (__libc_atexit, (void)) +/* initialise the processing complete flag to 0 */ +int __exit_funcs_done = 0; /* Call all functions registered with `atexit' and `on_exit', in the reverse of the order in which they were registered @@ -44,14 +47,30 @@ __run_exit_handlers (int status, struct exit_function_list **listp, the functions registered with `atexit' and `on_exit'. We call everyone on the list and use the status value in the last exit (). */ - while (*listp != NULL) + while (true) { - struct exit_function_list *cur = *listp; + struct exit_function_list *cur; + + restart: + __libc_lock_lock (__exit_funcs_lock); + cur = *listp; + + if (cur == NULL) + { + /* Exit processing complete. We will not allow any more + atexit/on_exit registrations. */ + __exit_funcs_done = 1; + __libc_lock_unlock (__exit_funcs_lock); + break; + } while (cur->idx > 0) { const struct exit_function *const f = &cur->fns[--cur->idx]; + const uint64_t new_exitfn_called = __new_exitfn_called; + + __libc_lock_unlock (__exit_funcs_lock); switch (f->flavor) { void (*atfct) (void); @@ -83,6 +102,15 @@ __run_exit_handlers (int status, struct exit_function_list **listp, cxafct (f->func.cxa.arg, status); break; } + __libc_lock_lock (__exit_funcs_lock); + + if (__glibc_unlikely (new_exitfn_called != __new_exitfn_called)) + { + /* The last exit function, or another thread, has registered + more exit functions. Start the loop over. */ + __libc_lock_unlock (__exit_funcs_lock); + goto restart; + } } *listp = cur->next; @@ -90,6 +118,8 @@ __run_exit_handlers (int status, struct exit_function_list **listp, /* Don't free the last element in the chain, this is the statically allocate element. */ free (cur); + + __libc_lock_unlock (__exit_funcs_lock); } if (run_list_atexit) diff --git a/stdlib/exit.h b/stdlib/exit.h index 7f2e679246..023e81b83f 100644 --- a/stdlib/exit.h +++ b/stdlib/exit.h @@ -20,6 +20,7 @@ #include #include +#include enum { @@ -62,6 +63,10 @@ extern struct exit_function_list *__quick_exit_funcs attribute_hidden; extern struct exit_function *__new_exitfn (struct exit_function_list **listp); extern uint64_t __new_exitfn_called attribute_hidden; +__libc_lock_define (extern, __exit_funcs_lock); + +/* flag to mark that all registered atexit/onexit handlers are called */ +extern int __exit_funcs_done attribute_hidden; extern void __run_exit_handlers (int status, struct exit_function_list **listp, diff --git a/stdlib/on_exit.c b/stdlib/on_exit.c index 83845e76d8..2db3063db9 100644 --- a/stdlib/on_exit.c +++ b/stdlib/on_exit.c @@ -24,10 +24,16 @@ int __on_exit (void (*func) (int status, void *arg), void *arg) { - struct exit_function *new = __new_exitfn (&__exit_funcs); + struct exit_function *new; + + __libc_lock_lock (__exit_funcs_lock); + new = __new_exitfn (&__exit_funcs); if (new == NULL) - return -1; + { + __libc_lock_unlock (__exit_funcs_lock); + return -1; + } #ifdef PTR_MANGLE PTR_MANGLE (func); @@ -36,6 +42,7 @@ __on_exit (void (*func) (int status, void *arg), void *arg) new->func.on.arg = arg; atomic_write_barrier (); new->flavor = ef_on; + __libc_lock_unlock (__exit_funcs_lock); return 0; } weak_alias (__on_exit, on_exit) diff --git a/stdlib/test-__cxa_atexit-race.c b/stdlib/test-__cxa_atexit-race.c new file mode 100644 index 0000000000..b86f6ce212 --- /dev/null +++ b/stdlib/test-__cxa_atexit-race.c @@ -0,0 +1,34 @@ +/* A test for __cxa_atexit/exit race from bz14333. + + Copyright (C) 2017 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 + . */ + +/* This file must be run from within a directory called "stdlib". */ + +#include + +#define CALL_ATEXIT __cxa_atexit (&no_op, NULL, NULL) +#define CALL_EXIT exit (0) + +int __cxa_atexit (void (*func) (void *), void *arg, void *d); + +static void +no_op (void *ignored) +{ +} + +#include diff --git a/stdlib/test-at_quick_exit-race.c b/stdlib/test-at_quick_exit-race.c new file mode 100644 index 0000000000..2521a6b77c --- /dev/null +++ b/stdlib/test-at_quick_exit-race.c @@ -0,0 +1,30 @@ +/* A test for at_quick_exit/quick_exit race from bz14333. + + Copyright (C) 2017 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 + . */ + +/* This file must be run from within a directory called "stdlib". */ + +#define CALL_ATEXIT at_quick_exit (&no_op) +#define CALL_EXIT quick_exit (0) + +static void +no_op (void) +{ +} + +#include diff --git a/stdlib/test-atexit-race-common.c b/stdlib/test-atexit-race-common.c new file mode 100644 index 0000000000..c4cbd9e592 --- /dev/null +++ b/stdlib/test-atexit-race-common.c @@ -0,0 +1,62 @@ +/* Support file for atexit/exit, at_quick_exit/quick_exit, etc. race tests + from bz14333. + + Copyright (C) 2017 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 + . */ + +/* This file must be run from within a directory called "stdlib". */ + +#if !defined(CALL_EXIT) || !defined(CALL_ATEXIT) +#error Must define CALL_EXIT and CALL_ATEXIT before using this file. +#endif + +#include +#include +#include + +const size_t kNumThreads = 1024; +const size_t kNumHandlers = 1024; + +static void * +threadfunc (void *unused) +{ + size_t i; + for (i = 0; i < kNumHandlers; ++i) { + CALL_ATEXIT; + } + return NULL; +} + +static int +do_test (void) +{ + size_t i; + pthread_t thr; + pthread_attr_t attr; + + pthread_attr_init (&attr); + pthread_attr_setdetachstate (&attr, 1); + + for (i = 0; i < kNumThreads; ++i) { + pthread_create (&thr, &attr, threadfunc, NULL); + } + + CALL_EXIT; +} + +#define TEST_FUNCTION do_test +#include diff --git a/stdlib/test-atexit-race.c b/stdlib/test-atexit-race.c new file mode 100644 index 0000000000..b183ecfd7e --- /dev/null +++ b/stdlib/test-atexit-race.c @@ -0,0 +1,30 @@ +/* A test for atexit/exit race from bz14333. + + Copyright (C) 2017 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 + . */ + +/* This file must be run from within a directory called "stdlib". */ + +#define CALL_ATEXIT atexit (&no_op) +#define CALL_EXIT exit (0) + +static void +no_op (void) +{ +} + +#include