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DescriptionEdjunior Barbosa Machado
2019-01-02 13:12:54 UTC
Created attachment 1517950[details]
full strace log output on aarch64
Description of problem:
Latest strace-4.24-3.el8 occasionally reports '<ptrace(SYSCALL):No such process>' on getuid() calls when running the testcase below:
[root@qualcomm-amberwing-rep-10 ~]# cat many_looping_threads.c
#include <stdio.h>
#include <pthread.h>
#include <unistd.h>
#include <sys/types.h>
#include <signal.h>
#include <stdlib.h>
static int thd_no;
static void *sub_thd(void *c)
{
fprintf(stderr, "sub-thread %d created\n", ++thd_no);
for (;;)
getuid();
return NULL;
}
int main(int argc, char *argv[])
{
int i;
pthread_t *thd;
int num_threads = 1;
if (argv[1])
num_threads = atoi(argv[1]);
thd = malloc(num_threads * sizeof(thd[0]));
fprintf(stderr, "test start, num_threads:%d...\n", num_threads);
for (i = 0; i < num_threads; i++) {
pthread_create(&thd[i], NULL, sub_thd, NULL);
fprintf(stderr, "after pthread_create\n");
}
/* Exit. This kills all threads */
return 0;
}
[root@qualcomm-amberwing-rep-10 ~]# gcc many_looping_threads.c -o many_looping_threads -lpthread
[root@qualcomm-amberwing-rep-10 ~]# strace -f -o strace-log.log ./many_looping_threads 20
test start, num_threads:20...
after pthread_create
sub-thread 1 created
sub-thread 2 created
after pthread_create
after pthread_create
sub-thread 3 created
after pthread_create
sub-thread 4 created
after pthread_create
sub-thread 5 created
after pthread_create
sub-thread 6 created
after pthread_create
sub-thread 7 created
after pthread_create
sub-thread 8 created
after pthread_create
sub-thread 9 created
after pthread_create
sub-thread 10 created
after pthread_create
sub-thread 11 created
after pthread_create
sub-thread 12 created
after pthread_create
sub-thread 13 created
after pthread_create
sub-thread 14 created
after pthread_create
sub-thread 15 created
after pthread_create
sub-thread 16 created
after pthread_create
sub-thread 17 created
after pthread_create
sub-thread 18 created
after pthread_create
sub-thread 19 created
after pthread_create
sub-thread 20 created
[root@qualcomm-amberwing-rep-10 ~]# grep 'No such process' strace-log.log -C3
22468 getuid( <unfinished ...>
22467 exit_group(0 <unfinished ...>
22487 <... write resumed> ) = 22
22486 getuid( <ptrace(SYSCALL):No such process>
22485 <... getuid resumed> ) = ? <unavailable>
22484 ????( <unfinished ...>
22483 <... getuid resumed> ) = 0
The same tests also runs successfully sometimes, without any 'No such process' message.
Version-Release number of selected component (if applicable):
strace-4.24-3.el8
RHEL-8.0-20181220.1
How reproducible:
Occasionally
Comment 1Eugene Syromiatnikov
2019-01-29 14:04:40 UTC
I would say that this is not a bug, since the aforementioned ptrace(PTRACE_SYSCALL) error is genuinely possible when the process disappears between execution of the syscall entry code and an attempt to resume the tracee[1].
[1] https://gitlab.com/strace/strace/blob/v4.24/strace.c#L396
Comment 2Eugene Syromiatnikov
2019-02-11 18:26:11 UTC
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://access.redhat.com/errata/RHBA-2019:3642
Created attachment 1517950 [details] full strace log output on aarch64 Description of problem: Latest strace-4.24-3.el8 occasionally reports '<ptrace(SYSCALL):No such process>' on getuid() calls when running the testcase below: [root@qualcomm-amberwing-rep-10 ~]# cat many_looping_threads.c #include <stdio.h> #include <pthread.h> #include <unistd.h> #include <sys/types.h> #include <signal.h> #include <stdlib.h> static int thd_no; static void *sub_thd(void *c) { fprintf(stderr, "sub-thread %d created\n", ++thd_no); for (;;) getuid(); return NULL; } int main(int argc, char *argv[]) { int i; pthread_t *thd; int num_threads = 1; if (argv[1]) num_threads = atoi(argv[1]); thd = malloc(num_threads * sizeof(thd[0])); fprintf(stderr, "test start, num_threads:%d...\n", num_threads); for (i = 0; i < num_threads; i++) { pthread_create(&thd[i], NULL, sub_thd, NULL); fprintf(stderr, "after pthread_create\n"); } /* Exit. This kills all threads */ return 0; } [root@qualcomm-amberwing-rep-10 ~]# gcc many_looping_threads.c -o many_looping_threads -lpthread [root@qualcomm-amberwing-rep-10 ~]# strace -f -o strace-log.log ./many_looping_threads 20 test start, num_threads:20... after pthread_create sub-thread 1 created sub-thread 2 created after pthread_create after pthread_create sub-thread 3 created after pthread_create sub-thread 4 created after pthread_create sub-thread 5 created after pthread_create sub-thread 6 created after pthread_create sub-thread 7 created after pthread_create sub-thread 8 created after pthread_create sub-thread 9 created after pthread_create sub-thread 10 created after pthread_create sub-thread 11 created after pthread_create sub-thread 12 created after pthread_create sub-thread 13 created after pthread_create sub-thread 14 created after pthread_create sub-thread 15 created after pthread_create sub-thread 16 created after pthread_create sub-thread 17 created after pthread_create sub-thread 18 created after pthread_create sub-thread 19 created after pthread_create sub-thread 20 created [root@qualcomm-amberwing-rep-10 ~]# grep 'No such process' strace-log.log -C3 22468 getuid( <unfinished ...> 22467 exit_group(0 <unfinished ...> 22487 <... write resumed> ) = 22 22486 getuid( <ptrace(SYSCALL):No such process> 22485 <... getuid resumed> ) = ? <unavailable> 22484 ????( <unfinished ...> 22483 <... getuid resumed> ) = 0 The same tests also runs successfully sometimes, without any 'No such process' message. Version-Release number of selected component (if applicable): strace-4.24-3.el8 RHEL-8.0-20181220.1 How reproducible: Occasionally