[PATCH 1/2] posix: Correctly enable/disable cancellation on Linux posix_spawn
Adhemerval Zanella
adhemerval.zanella@linaro.org
Tue Sep 20 18:17:00 GMT 2016
If no one opposes I will commit it shortly.
On 14/09/2016 15:56, Adhemerval Zanella wrote:
> This patch correctly enable and disable asynchronous cancellation on
> Linux posix_spawn. Current code invert the logic by enabling and
> disabling instead. A new test that checks if posix_spawn is not in fact
> a cancellation entrypoint is added.
>
> Checked on x86_64, i686, powerpc64le, and aarch64.
>
> * nptl/Makefile (tests): Add tst-exec5.
> * nptl/tst-exec5.c: New file.
> * sysdeps/unix/sysv/linux/spawni.c (__spawni): Correctly enable and disable
> asynchronous cancellation.
> ---
> nptl/Makefile | 2 +-
> nptl/tst-exec5.c | 200 +++++++++++++++++++++++++++++++++++++++
> sysdeps/unix/sysv/linux/spawni.c | 6 +-
> 4 files changed, 212 insertions(+), 3 deletions(-)
> create mode 100644 nptl/tst-exec5.c
>
> diff --git a/nptl/Makefile b/nptl/Makefile
> index 2ddcd2b..390e1f7 100644
> --- a/nptl/Makefile
> +++ b/nptl/Makefile
> @@ -268,7 +268,7 @@ tests = tst-typesizes \
> tst-flock1 tst-flock2 \
> tst-signal1 tst-signal2 tst-signal3 tst-signal4 tst-signal5 \
> tst-signal6 tst-signal7 \
> - tst-exec1 tst-exec2 tst-exec3 tst-exec4 \
> + tst-exec1 tst-exec2 tst-exec3 tst-exec4 tst-exec5 \
> tst-exit1 tst-exit2 tst-exit3 \
> tst-stdio1 tst-stdio2 \
> tst-stack1 tst-stack2 tst-stack3 tst-stack4 tst-pthread-getattr \
> diff --git a/nptl/tst-exec5.c b/nptl/tst-exec5.c
> new file mode 100644
> index 0000000..5527b23
> --- /dev/null
> +++ b/nptl/tst-exec5.c
> @@ -0,0 +1,200 @@
> +/* Check if posix_spawn does not act as a cancellation entrypoint.
> + Copyright (C) 2016 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 <errno.h>
> +#include <paths.h>
> +#include <pthread.h>
> +#include <signal.h>
> +#include <spawn.h>
> +#include <stdbool.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <unistd.h>
> +#include <sys/wait.h>
> +
> +static pthread_barrier_t b;
> +
> +static struct thread_args
> +{
> + pid_t pid;
> + int fd[2];
> +} targ;
> +
> +static void *
> +tf (void *arg)
> +{
> + int e = pthread_barrier_wait (&b);
> + if (e != 0 && e != PTHREAD_BARRIER_SERIAL_THREAD)
> + {
> + puts ("error: pthread_barrier_wait failed");
> + exit (1);
> + }
> +
> + posix_spawn_file_actions_t a;
> + if (posix_spawn_file_actions_init (&a) != 0)
> + {
> + puts ("error: spawn_file_actions_init failed");
> + exit (1);
> + }
> +
> + if (posix_spawn_file_actions_adddup2 (&a, targ.fd[1], STDOUT_FILENO) != 0)
> + {
> + puts ("error: spawn_file_actions_adddup2 failed");
> + exit (1);
> + }
> +
> + if (posix_spawn_file_actions_addclose (&a, targ.fd[0]) != 0)
> + {
> + puts ("error: spawn_file_actions_addclose");
> + exit (1);
> + }
> +
> + char *argv[] = { (char *) _PATH_BSHELL, (char *) "-c", (char *) "echo $$",
> + NULL };
> + if (posix_spawn (&targ.pid, _PATH_BSHELL, &a, NULL, argv, NULL) != 0)
> + {
> + puts ("error: spawn failed");
> + exit (1);
> + }
> +
> + return NULL;
> +}
> +
> +
> +static int
> +do_test (void)
> +{
> + /* The test basically pipes a 'echo $$' created by a thread with a
> + cancellation pending. It then checks if the thread is not
> + cancelled, the process is created, and if the output is the expected
> + one (the process pid). */
> +
> + if (pipe (targ.fd) != 0)
> + {
> + puts ("error: pipe failed");
> + exit (1);
> + }
> +
> + /* Not interested in knowing when the pipe is closed. */
> + if (sigignore (SIGPIPE) != 0)
> + {
> + puts ("error: sigignore failed");
> + exit (1);
> + }
> +
> + if (pthread_barrier_init (&b, NULL, 2) != 0)
> + {
> + puts ("error: pthread_barrier_init failed");
> + exit (1);
> + }
> +
> + pthread_t th;
> + if (pthread_create (&th, NULL, tf, &targ) != 0)
> + {
> + puts ("error: pthread_create failed");
> + exit (1);
> + }
> +
> + if (pthread_cancel (th) != 0)
> + {
> + puts ("error: pthread_cancel failed");
> + return 1;
> + }
> +
> + int e = pthread_barrier_wait (&b);
> + if (e != 0 && e != PTHREAD_BARRIER_SERIAL_THREAD)
> + {
> + puts ("error: pthread_barrier_wait failed");
> + exit (1);
> + }
> +
> + void *r;
> + if (pthread_join (th, &r) != 0)
> + {
> + puts ("error: pthread_join failed");
> + exit (1);
> + }
> +
> + if (r == PTHREAD_CANCELED)
> + {
> + puts ("error: thread cancelled");
> + exit (1);
> + }
> +
> + close (targ.fd[1]);
> +
> + /* The spawn_posix pid should be set by thread, check if it was executed
> + correctly and with expected output. */
> +
> + char buf[64];
> + ssize_t n;
> + bool seen_pid = false;
> + while (TEMP_FAILURE_RETRY ((n = read (targ.fd[0], buf, sizeof (buf)))) > 0)
> + {
> + /* We only expect to read the PID. */
> + char *endp;
> + long int rpid = strtol (buf, &endp, 10);
> +
> + if (*endp != '\n')
> + {
> + printf ("error: didn't parse whole line: \"%s\"\n", buf);
> + exit (1);
> + }
> + if (endp == buf)
> + {
> + puts ("error: read empty line");
> + exit (1);
> + }
> +
> + if (rpid != targ.pid)
> + {
> + printf ("error: found \"%s\", expected PID %ld\n", buf,
> + (long int) targ.pid);
> + exit (1);
> + }
> +
> + if (seen_pid)
> + {
> + puts ("error: found more than one PID line");
> + exit (1);
> + }
> +
> + seen_pid = true;
> + }
> +
> + close (targ.fd[0]);
> +
> + int status;
> + int err = waitpid (targ.pid, &status, 0);
> + if (err != targ.pid)
> + {
> + puts ("errnor: waitpid failed");
> + exit (1);
> + }
> +
> + if (!seen_pid)
> + {
> + puts ("error: didn't get PID");
> + exit (1);
> + }
> +
> + return 0;
> +}
> +
> +#define TEST_FUNCTION do_test ()
> +#include <test-skeleton.c>
> diff --git a/sysdeps/unix/sysv/linux/spawni.c b/sysdeps/unix/sysv/linux/spawni.c
> index 0b76657..f7cb96f 100644
> --- a/sysdeps/unix/sysv/linux/spawni.c
> +++ b/sysdeps/unix/sysv/linux/spawni.c
> @@ -317,7 +317,9 @@ __spawnix (pid_t * pid, const char *file,
> return errno;
>
> /* Disable asynchronous cancellation. */
> - int cs = LIBC_CANCEL_ASYNC ();
> + int state;
> + __libc_ptf_call (__pthread_setcancelstate,
> + (PTHREAD_CANCEL_DISABLE, &state), 0);
>
> args.file = file;
> args.exec = exec;
> @@ -357,7 +359,7 @@ __spawnix (pid_t * pid, const char *file,
>
> __sigprocmask (SIG_SETMASK, &args.oldmask, 0);
>
> - LIBC_CANCEL_RESET (cs);
> + __libc_ptf_call (__pthread_setcancelstate, (state, NULL), 0);
>
> return ec;
> }
>
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