Patchwork [1/3] support: Add support_process_state_wait

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Submitter Adhemerval Zanella Netto
Date Nov. 20, 2019, 2:15 p.m.
Message ID <20191120141535.5303-1-adhemerval.zanella@linaro.org>
Download mbox | patch
Permalink /patch/36060/
State New
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Comments

Adhemerval Zanella Netto - Nov. 20, 2019, 2:15 p.m.
It allows parent process to wait for children state using a polling
strategy over procfs on Linux.  The polling is used over ptrace to
avoid the need to handle signals on the target pid and to handle some
system specific limitations (such as YAMA).

The polling has some limitations, such as resource consumption due
the procfs read in a loop and the lack of synchronization after the
state is obtained.

The interface idea is to simplify some sleep synchronization in waitid
tests.
---
 support/Makefile                    |   2 +
 support/process_state.h             |  41 +++++++++++
 support/support_process_state.c     |  89 ++++++++++++++++++++++++
 support/tst-support-process_state.c | 101 ++++++++++++++++++++++++++++
 4 files changed, 233 insertions(+)
 create mode 100644 support/process_state.h
 create mode 100644 support/support_process_state.c
 create mode 100644 support/tst-support-process_state.c

Patch

diff --git a/support/Makefile b/support/Makefile
index 23c6d74627..b0d28200af 100644
--- a/support/Makefile
+++ b/support/Makefile
@@ -56,6 +56,7 @@  libsupport-routines = \
   support_format_hostent \
   support_format_netent \
   support_isolate_in_subprocess \
+  support_process_state \
   support_ptrace \
   support_openpty \
   support_paths \
@@ -223,6 +224,7 @@  tests = \
   tst-support_capture_subprocess \
   tst-support_descriptors \
   tst-support_format_dns_packet \
+  tst-support-process_state \
   tst-support_quote_blob \
   tst-support_quote_string \
   tst-support_record_failure \
diff --git a/support/process_state.h b/support/process_state.h
new file mode 100644
index 0000000000..d616f0e3e6
--- /dev/null
+++ b/support/process_state.h
@@ -0,0 +1,41 @@ 
+/* Wait for process state.
+   Copyright (C) 2019 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
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef SUPPORT_PROCESS_STATE_H
+#define SUPPORT_PROCESS_STATE_H
+
+#include <sys/types.h>
+
+enum process_state_t
+{
+  process_state_running      = 0x01,  /* R (running)  */
+  process_state_sleeping     = 0x02,  /* S (sleeping)  */
+  process_state_disk_sleep   = 0x04,  /* D (disk sleep)  */
+  process_state_stopped      = 0x08,  /* T (stopped)  */
+  process_state_tracing_stop = 0x10,  /* t (tracing stop)  */
+  process_state_dead         = 0x20,  /* X (dead)  */
+  process_state_zombie       = 0x40,  /* Z (zombie)  */
+  process_state_parked       = 0x80,  /* P (parked)  */
+};
+
+/* Wait for process PID to reach state STATE.  It can be a combination of
+   multiple possible states ('process_state_running | process_state_sleeping')
+   where the function return when any of these state are observed.  */
+void support_process_state_wait (pid_t pid, enum process_state_t state);
+
+#endif
diff --git a/support/support_process_state.c b/support/support_process_state.c
new file mode 100644
index 0000000000..77c684c49c
--- /dev/null
+++ b/support/support_process_state.c
@@ -0,0 +1,89 @@ 
+/* Wait for process state.
+   Copyright (C) 2019 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
+   <https://www.gnu.org/licenses/>.  */
+
+#include <stdio.h>
+#include <fcntl.h>
+#include <time.h>
+
+#include <array_length.h>
+
+#include <support/process_state.h>
+#include <support/xunistd.h>
+#include <support/check.h>
+
+void
+support_process_state_wait (pid_t pid, enum process_state_t state)
+{
+#ifdef __linux__
+  /* For Linux it does a polling check on /proc/<pid>/status checking on
+     third field.  */
+
+  /* It mimics the kernel states from fs/proc/array.c  */
+  static struct process_states_t
+  {
+    enum process_state_t s;
+    char v;
+  } process_states[] = {
+    { process_state_running,      'R' },
+    { process_state_sleeping,     'S' },
+    { process_state_disk_sleep,   'D' },
+    { process_state_stopped,      'T' },
+    { process_state_tracing_stop, 't' },
+    { process_state_dead,         'X' },
+    { process_state_zombie,       'Z' },
+    { process_state_parked,       'P' },
+  };
+
+  char proc_path[sizeof ("/proc/" + 3) * sizeof (pid_t) + sizeof ("/stat")
+		 + 1];
+  snprintf (proc_path, sizeof (proc_path), "/proc/%i/stat", pid);
+
+  int fd = xopen (proc_path, O_RDONLY, 0600);
+
+  char statbuf[3 * sizeof (pid_t)  /* pid.  */
+               + 2                 /* ' (' */
+               + 64                /* task name.  */
+               + 2                 /* ' )'  */
+               + 1                 /* <state>, 1 char.  */
+               + 1];               /* Final \0.  */
+  for (;;)
+    {
+      ssize_t ret = read (fd, statbuf, sizeof (statbuf) - 1);
+      TEST_VERIFY (ret >= 0);
+      statbuf[ret] = '\0';
+
+      char cur_state;
+      int sret = sscanf (statbuf, "%*i %*s %c", &cur_state);
+      TEST_VERIFY (sret == 1);
+
+      for (size_t i = 0; i < array_length (process_states); ++i)
+	if (state & process_states[i].s && cur_state == process_states[i].v)
+	  {
+	    close (fd);
+	    return;
+	  }
+
+      xlseek (fd, 0, SEEK_SET);
+      nanosleep (&(struct timespec) { 0, 10000000 }, NULL);
+    }
+
+  close (fd);
+#else
+  sleep (2);
+#endif
+}
diff --git a/support/tst-support-process_state.c b/support/tst-support-process_state.c
new file mode 100644
index 0000000000..3482f12fa5
--- /dev/null
+++ b/support/tst-support-process_state.c
@@ -0,0 +1,101 @@ 
+/* Wait for process state tests.
+   Copyright (C) 2019 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
+   <https://www.gnu.org/licenses/>.  */
+
+#include <stdio.h>
+#include <sys/wait.h>
+#include <unistd.h>
+#include <errno.h>
+
+#include <support/test-driver.h>
+#include <support/process_state.h>
+#include <support/check.h>
+#include <support/xsignal.h>
+#include <support/xunistd.h>
+
+static void
+sigusr1_handler (int signo)
+{
+}
+
+static void
+test_child (void)
+{
+  xsignal (SIGUSR1, sigusr1_handler);
+
+  raise (SIGSTOP);
+
+  TEST_COMPARE (pause (), -1);
+  TEST_COMPARE (errno, EINTR);
+
+  while (1)
+    asm ("");
+}
+
+static int
+do_test (void)
+{
+  pid_t pid = xfork ();
+  if (pid == 0)
+    {
+      test_child ();
+      _exit (127);
+    }
+
+  /* Adding process_state_tracing_stop ('t') allows the test to work under
+     trace programs such as ptrace.  */
+  enum process_state_t stop_state = process_state_stopped
+				    | process_state_tracing_stop;
+
+  if (test_verbose)
+    printf ("info: waiting pid %d, state_stopped/state_tracing_stop\n",
+	    (int) pid);
+  support_process_state_wait (pid, stop_state);
+
+  if (kill (pid, SIGCONT) != 0)
+    FAIL_RET ("kill (%d, SIGCONT): %m\n", pid);
+
+  if (test_verbose)
+    printf ("info: waiting pid %d, state_sleeping\n", (int) pid);
+  support_process_state_wait (pid, process_state_sleeping);
+
+  if (kill (pid, SIGUSR1) != 0)
+    FAIL_RET ("kill (%d, SIGUSR1): %m\n", pid);
+
+  if (test_verbose)
+    printf ("info: waiting pid %d, state_running\n", (int) pid);
+  support_process_state_wait (pid, process_state_running);
+
+  if (kill (pid, SIGKILL) != 0)
+    FAIL_RET ("kill (%d, SIGKILL): %m\n", pid);
+
+  if (test_verbose)
+    printf ("info: waiting pid %d, state_zombie\n", (int) pid);
+  support_process_state_wait (pid, process_state_zombie);
+
+  siginfo_t info;
+  int r = waitid (P_PID, pid, &info, WEXITED);
+  TEST_COMPARE (r, 0);
+  TEST_COMPARE (info.si_signo, SIGCHLD);
+  TEST_COMPARE (info.si_code, CLD_KILLED);
+  TEST_COMPARE (info.si_status, SIGKILL);
+  TEST_COMPARE (info.si_pid, pid);
+
+  return 0;
+}
+
+#include <support/test-driver.c>