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tst-mallocfork2: Fix race condition, use fewer resources 

The first SIGUSR1 signal could arrive when sigusr1_sender_pid
was still 0.  As a result, kill would send SIGSTOP to the
entire process group.  This would cause the test to hang before
printing any output.

This commit also adds a sched_yield to the signal source, so that
it does not flood the parent process with signals it has never a
chance to handle.

Even with these changes, tst-mallocfork2 still fails reliably
after the fix in commit commit 56290d6e76
(Increase fork signal safety for single-threaded processes) is
backed out.
This commit is contained in:
Florian Weimer 2016-05-13 16:55:01 +02:00
parent fdbdbc83a5
commit e2cd73a2cc
2 changed files with 14 additions and 1 deletions
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7
ChangeLog
View File

@ -1,3 +1,10 @@
2016-05-13 Florian Weimer <fweimer@redhat.com>
Fix race condition in tst-mallocfork2, use fewer resources.
* malloc/tst-mallocfork2.c (sigusr1_handler): Do not send SIGSTOP
to current process group.
(signal_sender): Yield in the non-sleeping case.
2016-05-13 Joseph Myers <joseph@codesourcery.com>
* conform/data/stdlib.h-data (a64l): Do not expect for [XPG3].

8
malloc/tst-mallocfork2.c
View File

@ -25,6 +25,7 @@
still make fork unsafe, even in single-threaded processes. */
#include <errno.h>
#include <sched.h>
#include <signal.h>
#include <stdbool.h>
#include <stdio.h>
@ -70,7 +71,9 @@ sigusr1_handler (int signo)
signals from the subprocess. */
if (sigusr1_received)
return;
if (kill (sigusr1_sender_pid, SIGSTOP) != 0)
/* sigusr1_sender_pid might not be initialized in the parent when
the first SIGUSR1 signal arrives. */
if (sigusr1_sender_pid > 0 && kill (sigusr1_sender_pid, SIGSTOP) != 0)
{
write_message ("error: kill (SIGSTOP)\n");
abort ();
@ -123,6 +126,9 @@ signal_sender (int signo, bool sleep)
}
if (sleep)
usleep (1 * 1000 * 1000);
else
/* Reduce the rate at which we send signals. */
sched_yield ();
}
}