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Re: [PATCH v2 2/3] PR remote/19496, interrupted syscall in forking-threads-plus-bkpt
- From: Don Breazeal <donb at codesourcery dot com>
- To: <gdb-patches at sourceware dot org>, <palves at redhat dot com>
- Date: Wed, 16 Mar 2016 11:25:50 -0700
- Subject: Re: [PATCH v2 2/3] PR remote/19496, interrupted syscall in forking-threads-plus-bkpt
- Authentication-results: sourceware.org; auth=none
On 3/15/2016 5:55 AM, Pedro Alves wrote:
> Hi Don,
>
> On 02/11/2016 12:28 AM, Don Breazeal wrote:
>
---snip---
>
> Use with_timeout_factor instead so that the timeout is properly restored,
> and put it around the problematic test, only, instead of basically
> around the whole test case. I think that'll be the "inferior 1 exited"
> test?
Thanks Pedro. This is done in the patch below. OK to push?
--Don
This patch addresses "fork:Interrupted system call" (or wait:) failures
in gdb.threads/forking-threads-plus-breakpoint.exp.
The test program spawns ten threads, each of which do ten fork/waitpid
sequences. The cause of the problem was that when one of the fork
children exited before the corresponding fork parent could initiate its
waitpid for that child, a SIGCHLD and/or SIGSTOP was delivered and
interrupted a fork or waitpid in another thread.
The fix was to wrap the system calls in a loop to retry the call if
it was interrupted, like:
do
{
pid = fork ();
}
while (pid == -1 && errno == EINTR);
Since this is a Linux-only test I figure it is OK to use errno and EINTR.
I tried a number of alternative fixes using SIG_IGN, SA_RESTART,
pthread_sigblock, and bsd_signal, but none of these worked as well.
Tested on Nios II Linux target with x86 Linux host.
gdb/testsuite/ChangeLog:
2016-03-16 Don Breazeal <donb@codesourcery.com>
* gdb.threads/forking-threads-plus-breakpoint.c (thread_forks):
Retry fork and waitpid on interrupted system call errors.
* gdb.threads/forking-threads-plus-breakpoint.exp: (do_test):
Use with_timeout_factor to increase timeout to 90.
---
.../gdb.threads/forking-threads-plus-breakpoint.c | 14 +++++++++-
.../forking-threads-plus-breakpoint.exp | 27 +++++++++++---------
2 files changed, 27 insertions(+), 14 deletions(-)
diff --git a/gdb/testsuite/gdb.threads/forking-threads-plus-breakpoint.c b/gdb/testsuite/gdb.threads/forking-threads-plus-breakpoint.c
index fc64d93..c169e18 100644
--- a/gdb/testsuite/gdb.threads/forking-threads-plus-breakpoint.c
+++ b/gdb/testsuite/gdb.threads/forking-threads-plus-breakpoint.c
@@ -22,6 +22,7 @@
#include <sys/types.h>
#include <sys/wait.h>
#include <stdlib.h>
+#include <errno.h>
/* Number of threads. Each thread continuously spawns a fork and wait
for it. If we have another thread continuously start a step over,
@@ -49,14 +50,23 @@ thread_forks (void *arg)
{
pid_t pid;
- pid = fork ();
+ do
+ {
+ pid = fork ();
+ }
+ while (pid == -1 && errno == EINTR);
if (pid > 0)
{
int status;
/* Parent. */
- pid = waitpid (pid, &status, 0);
+ do
+ {
+ pid = waitpid (pid, &status, 0);
+ }
+ while (pid == -1 && errno == EINTR);
+
if (pid == -1)
{
perror ("wait");
diff --git a/gdb/testsuite/gdb.threads/forking-threads-plus-breakpoint.exp b/gdb/testsuite/gdb.threads/forking-threads-plus-breakpoint.exp
index 3d8b308..9c700bf 100644
--- a/gdb/testsuite/gdb.threads/forking-threads-plus-breakpoint.exp
+++ b/gdb/testsuite/gdb.threads/forking-threads-plus-breakpoint.exp
@@ -72,6 +72,7 @@ proc do_test { cond_bp_target detach_on_fork displaced } {
global decimal gdb_prompt
global linenum
global is_remote_target
+ global timeout
set saved_gdbflags $GDBFLAGS
set GDBFLAGS [concat $GDBFLAGS " -ex \"set non-stop on\""]
@@ -115,18 +116,20 @@ proc do_test { cond_bp_target detach_on_fork displaced } {
set fork_count 0
set ok 0
- set test "inferior 1 exited"
- gdb_test_multiple "" $test {
- -re "Inferior 1 \(\[^\r\n\]+\) exited normally" {
- set ok 1
- pass $test
- }
- -re "Inferior $decimal \(\[^\r\n\]+\) exited normally" {
- incr fork_count
- if {$fork_count <= 100} {
- exp_continue
- } else {
- fail "$test (too many forks)"
+ with_timeout_factor 90 {
+ set test "inferior 1 exited"
+ gdb_test_multiple "" $test {
+ -re "Inferior 1 \(\[^\r\n\]+\) exited normally" {
+ set ok 1
+ pass $test
+ }
+ -re "Inferior $decimal \(\[^\r\n\]+\) exited normally" {
+ incr fork_count
+ if {$fork_count <= 100} {
+ exp_continue
+ } else {
+ fail "$test (too many forks)"
+ }
}
}
}
--
1.7.0.4