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malloc/tst-mallocfork2: Use process-shared barriers
This synchronization method has a lower overhead and makes it more likely that the signal arrives during one of the critical functions. Also test for fork deadlocks explicitly. Reviewed-by: Szabolcs Nagy <szabolcs.nagy@arm.com>
This commit is contained in:
Florian Weimer
parent
7621676f7a
commit
b2f601ba9a
20
ChangeLog
20
ChangeLog
@ -1,3 +1,23 @@
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2019-05-08 Florian Weimer <fweimer@redhat.com>
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malloc/tst-mallocfork2: Use process-shared barriers.
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* malloc/tst-mallocfork2.c: Switch to <support/test-driver.c>.
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(signal_count, sigusr1_sender_pid): Remove.
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(iterations): Define constant.
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(shared): New variable.
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(sigusr1_received): Update comment.
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(sigusr1_handler): Do not send SIGSTOP to the sender process.
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(signal_sender): Optional use barriers to avoid sending signals
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during irrelevant times.
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(do_it): Initialize variable shared. Use xfork for error
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checking. Launch multiple SIGUSR1-sending subprocesses. Limit
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the iteration count, independent of signal delivery. Check for
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deadlocks in fork. Introduce barriers for reducing signal
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traffic. Do not send SIGCONT to the SIGUSR1-sending processes;
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replaced by the barriers. Count signals during fork/free/malloc
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and report them.
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* malloc/Makefile (tst-mallocfork): Link with libpthread.
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2019-05-07 Joseph Myers <joseph@codesourcery.com>
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* sysdeps/unix/sysv/linux/syscall-names.list: Update kernel
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@ -252,3 +252,4 @@ $(objpfx)tst-dynarray-fail-mem.out: $(objpfx)tst-dynarray-fail.out
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$(objpfx)tst-malloc-tcache-leak: $(shared-thread-library)
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$(objpfx)tst-malloc_info: $(shared-thread-library)
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$(objpfx)tst-mallocfork2: $(shared-thread-library)
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@ -34,6 +34,11 @@
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#include <sys/wait.h>
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#include <time.h>
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#include <unistd.h>
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#include <array_length.h>
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#include <support/check.h>
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#include <support/support.h>
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#include <support/xthread.h>
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#include <support/xunistd.h>
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/* How many malloc objects to keep arond. */
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enum { malloc_objects = 1009 };
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@ -41,19 +46,16 @@ enum { malloc_objects = 1009 };
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/* The maximum size of an object. */
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enum { malloc_maximum_size = 70000 };
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/* How many signals need to be delivered before the test exits. */
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enum { signal_count = 1000 };
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/* How many iterations the test performs before exiting. */
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enum { iterations = 10000 };
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static int do_test (void);
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#define TIMEOUT 100
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#define TEST_FUNCTION do_test ()
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#include "../test-skeleton.c"
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/* Process ID of the subprocess which sends SIGUSR1 signals. */
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static pid_t sigusr1_sender_pid;
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/* Barrier for synchronization with the processes sending SIGUSR1
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signals, to make it more likely that the signals arrive during a
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fork/free/malloc call. */
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static struct { pthread_barrier_t barrier; } *shared;
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/* Set to 1 if SIGUSR1 is received. Used to detect a signal during
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malloc/free. */
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fork/free/malloc. */
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static volatile sig_atomic_t sigusr1_received;
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/* Periodically set to 1, to indicate that the process is making
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@ -63,17 +65,6 @@ static volatile sig_atomic_t progress_indicator = 1;
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static void
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sigusr1_handler (int signo)
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{
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/* Let the main program make progress, by temporarily suspending
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signals from the subprocess. */
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if (sigusr1_received)
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return;
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/* sigusr1_sender_pid might not be initialized in the parent when
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the first SIGUSR1 signal arrives. */
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if (sigusr1_sender_pid > 0 && kill (sigusr1_sender_pid, SIGSTOP) != 0)
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{
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write_message ("error: kill (SIGSTOP)\n");
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abort ();
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}
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sigusr1_received = 1;
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/* Perform a fork with a trivial subprocess. */
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@ -108,6 +99,8 @@ liveness_signal_handler (int signo)
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write_message ("warning: process seems to be stuck\n");
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}
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/* Send SIGNO to the parent process. If SLEEP, wait a second between
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signals, otherwise use barriers to delay sending signals. */
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static void
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__attribute__ ((noreturn))
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signal_sender (int signo, bool sleep)
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@ -115,6 +108,8 @@ signal_sender (int signo, bool sleep)
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pid_t target = getppid ();
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while (true)
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{
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if (!sleep)
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xpthread_barrier_wait (&shared->barrier);
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if (kill (target, signo) != 0)
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{
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dprintf (STDOUT_FILENO, "error: kill: %m\n");
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@ -123,14 +118,17 @@ signal_sender (int signo, bool sleep)
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if (sleep)
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usleep (1 * 1000 * 1000);
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else
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/* Reduce the rate at which we send signals. */
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sched_yield ();
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xpthread_barrier_wait (&shared->barrier);
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}
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}
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static int
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do_test (void)
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{
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/* shared->barrier is intialized along with sigusr1_sender_pids
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below. */
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shared = support_shared_allocate (sizeof (*shared));
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struct sigaction action =
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{
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.sa_handler = sigusr1_handler,
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@ -150,48 +148,74 @@ do_test (void)
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return 1;
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}
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pid_t sigusr2_sender_pid = fork ();
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pid_t sigusr2_sender_pid = xfork ();
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if (sigusr2_sender_pid == 0)
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signal_sender (SIGUSR2, true);
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sigusr1_sender_pid = fork ();
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if (sigusr1_sender_pid == 0)
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signal_sender (SIGUSR1, false);
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/* Send SIGUSR1 signals from several processes. Hopefully, one
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signal will hit one of the ciritical functions. Use a barrier to
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avoid sending signals while not running fork/free/malloc. */
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pid_t sigusr1_sender_pids[5];
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{
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pthread_barrierattr_t attr;
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xpthread_barrierattr_init (&attr);
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xpthread_barrierattr_setpshared (&attr, PTHREAD_PROCESS_SHARED);
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xpthread_barrier_init (&shared->barrier, &attr,
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array_length (sigusr1_sender_pids) + 1);
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xpthread_barrierattr_destroy (&attr);
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}
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for (size_t i = 0; i < array_length (sigusr1_sender_pids); ++i)
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{
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sigusr1_sender_pids[i] = fork ();
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if (sigusr1_sender_pids[i] == 0)
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signal_sender (SIGUSR1, false);
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}
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void *objects[malloc_objects] = {};
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unsigned signals = 0;
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unsigned int fork_signals = 0;
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unsigned int free_signals = 0;
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unsigned int malloc_signals = 0;
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unsigned seed = 1;
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time_t last_report = 0;
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while (signals < signal_count)
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for (int i = 0; i < iterations; ++i)
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{
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progress_indicator = 1;
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int slot = rand_r (&seed) % malloc_objects;
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size_t size = rand_r (&seed) % malloc_maximum_size;
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if (kill (sigusr1_sender_pid, SIGCONT) != 0)
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/* Occasionally do a fork first, to catch deadlocks there as
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well (see bug 24161). */
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bool do_fork = (rand_r (&seed) % 7) == 0;
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xpthread_barrier_wait (&shared->barrier);
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if (do_fork)
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{
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printf ("error: kill (SIGCONT): %m\n");
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signal (SIGUSR1, SIG_IGN);
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kill (sigusr1_sender_pid, SIGKILL);
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kill (sigusr2_sender_pid, SIGKILL);
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return 1;
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sigusr1_received = 0;
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pid_t pid = xfork ();
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if (sigusr1_received)
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++fork_signals;
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if (pid == 0)
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_exit (0);
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int status;
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int ret = TEMP_FAILURE_RETRY (waitpid (pid, &status, 0));
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if (ret < 0)
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FAIL_EXIT1 ("waitpid: %m");
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TEST_COMPARE (status, 0);
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}
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sigusr1_received = false;
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sigusr1_received = 0;
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free (objects[slot]);
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if (sigusr1_received)
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++free_signals;
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sigusr1_received = 0;
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objects[slot] = malloc (size);
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if (sigusr1_received)
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{
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++signals;
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time_t current = time (0);
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if (current != last_report)
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{
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printf ("info: SIGUSR1 signal count: %u\n", signals);
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last_report = current;
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}
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}
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++malloc_signals;
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xpthread_barrier_wait (&shared->barrier);
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if (objects[slot] == NULL)
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{
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printf ("error: malloc: %m\n");
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signal (SIGUSR1, SIG_IGN);
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kill (sigusr1_sender_pid, SIGKILL);
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for (size_t i = 0; i < array_length (sigusr1_sender_pids); ++i)
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kill (sigusr1_sender_pids[i], SIGKILL);
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kill (sigusr2_sender_pid, SIGKILL);
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return 1;
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}
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@ -201,11 +225,20 @@ do_test (void)
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for (int slot = 0; slot < malloc_objects; ++slot)
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free (objects[slot]);
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/* Terminate the signal-sending subprocess. The SIGUSR1 handler
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should no longer run because it uses sigusr1_sender_pid. */
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signal (SIGUSR1, SIG_IGN);
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kill (sigusr1_sender_pid, SIGKILL);
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for (size_t i = 0; i < array_length (sigusr1_sender_pids); ++i)
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kill (sigusr1_sender_pids[i], SIGKILL);
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kill (sigusr2_sender_pid, SIGKILL);
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printf ("info: signals received during fork: %u\n", fork_signals);
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printf ("info: signals received during free: %u\n", free_signals);
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printf ("info: signals received during malloc: %u\n", malloc_signals);
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/* Do not destroy the barrier because of the SIGKILL above, which
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may have left the barrier in an inconsistent state. */
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support_shared_free (shared);
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return 0;
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}
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#define TIMEOUT 100
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#include <support/test-driver.c>
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