Thanks, JC! Will add the comments.
Thanks,
- Jini.
On 12/13/2018 12:09 AM, JC Beyler wrote:
Hi Jini,
Fair enough, thanks for the explanation. It makes sense to me. I imagine
that it is a conservative approach, ie can't find the information then
assume still live.
Perhaps a small comment above the 'X'/'Z' test saying that the threads
are considered to be dead then?
And for the return perhaps say: the thread is considered live if the
state was not 'X'/'Z' or not found?
But those are really nits and no need to send another webrev for me!
Thanks!
Jc
On Wed, Dec 12, 2018 at 10:27 AM Jini George <jini.geo...@oracle.com
<mailto:jini.geo...@oracle.com>> wrote:
On 12/12/2018 10:47 PM, JC Beyler wrote:
> Hi Jini,
>
> Should your return not be return !found_state instead of false here:
>
> 257 if (!found_state) {
> 258 // Assuming the thread exists.
> 259 print_error("Could not find the 'State:' string in the
> /proc/%d/status file\n", pid);
> 260 }
> 261 fclose (fp);
> 262 return false;
>
> In your webrev.00 it was the case but now, you always return the
process
> does exist even if you have not found it.
I referred to the gdb sources to check what is done under this
scenario,
and in gdb, it is assumed that if the line beginning with 'State:' is
not found, the thread is alive. But to be frank, I don't know under
what
circumstances will we ever encounter such a scenario. Let me know if
you
don't agree with this.
> cf:
>
http://cr.openjdk.java.net/~jgeorge/8202884/webrev.00/src/jdk.hotspot.agent/linux/native/libsaproc/ps_proc.c.udiff.html
> vs
>
http://cr.openjdk.java.net/~jgeorge/8202884/webrev.02/src/jdk.hotspot.agent/linux/native/libsaproc/ps_proc.c.udiff.html
>
> Tiny nit: no need to check *space if you are using
isspace(*space) right
> after :)
Will change this. Thanks!
>
> Apart from the return question, the webrev looks good to me :-)
> Jc
Thank you again!
Jini
>
>
> On Wed, Dec 12, 2018 at 4:15 AM Jini George
<jini.geo...@oracle.com <mailto:jini.geo...@oracle.com>
> <mailto:jini.geo...@oracle.com <mailto:jini.geo...@oracle.com>>>
wrote:
>
> Thank you very much for looking into this, JC!
>
> I have a revised webrev addressing your comments at:
>
> http://cr.openjdk.java.net/~jgeorge/8202884/webrev.02/index.html
>
> Requesting one more review for this. My comments inline:
>
> On 12/12/2018 2:53 AM, JC Beyler wrote:
> > Hi Jini,
> >
> > I saw a few nits:
> >
>
http://cr.openjdk.java.net/~jgeorge/8202884/webrev.00/src/jdk.hotspot.agent/linux/native/libsaproc/libproc_impl.h.udiff.html
> > -> The comments are in the third person normally it
seems so
> it would
> > become (I also removed the s from threads):
> >
> > +// deletes a thread from the thread list
> Done.
> >
> >
>
http://cr.openjdk.java.net/~jgeorge/8202884/webrev.00/src/jdk.hotspot.agent/linux/native/libsaproc/libproc_impl.c.udiff.html
> > -> You added two empty lines it seems that could be removed
> Done.
> >
> >
> >
>
http://cr.openjdk.java.net/~jgeorge/8202884/webrev.00/src/jdk.hotspot.agent/linux/native/libsaproc/ps_proc.c.udiff.html
> > -> Is there a real reason to have both enums? We could
have a
> single
> > enum it seems and not lose too much
>
> You are right. I have done away with the WAITPID* enum.
>
> > -> you have a switch "
> > switch (errno) {"
> > -> Where really you could simplify the reading by
moving
> the
> > EINTR case outside with its continue
> > -> The switch could then remain as it was (though
you move
> > print_debug to print_error)
> > -> and just return in each cases
> I have changed this to:
>
> 206 } else {
> 207 switch (errno) {
> 208 case EINTR:
> 209 continue;
> 210 break;
> 211 case ECHILD:
> 212 print_debug("waitpid() failed. Child process
pid (%d)
> does
> not exist \n", pid);
> 213 return ATTACH_THREAD_DEAD;
> 214 case EINVAL:
> 215 print_error("waitpid() failed. Invalid options
> argument.\n");
> 216 return ATTACH_FAIL;
> 217 default:
> 218 print_error("waitpid() failed. Unexpected error
%d\n",
> errno);
> 219 return ATTACH_FAIL;
> 220 }
> 221 } // else
>
>
> >
> > -> if (strncmp (buf, "State:", 6) == 0) {
> > -> You use sizeof("State:") right below; perhaps
you could
> just
> > use " const char const state[] = "State:";" and use
> sizeof(state) and
> > for the string, it seems less error prone
> >
> > -> A minor "bug" is here:
> > + state = buf + sizeof ("State:");
> > -> You did a strncmp above but that only assures the
> start of
> > the string is "State:", technically the character after
the ':'
> is the
> > but it could only be that; sizeof("State:") is 7 and not 6. So
> you miss
> > one character when you are skipping spaces
> > -> It was probably ok because you always had at
least one
> > space, ie "State: "
>
> Thanks! I have made some changes here to use a const char
string and a
> variable to store the calculated length using strlen(). And I
am using
> isspace() now to skip spaces since tabs could also be used as a
> delimiter.
>
> > -> Extra space here before the '(': "sizeof (buf)"
> Done.
> >
> > Finally your return sequence for that method could be
simplified to:
> >
> > + if (!found_state) {
> > + print_error(" Could not find the State: string in the
status
> file
> > for pid %d\n", pid);
> > + }
> > + fclose (fp);
> > + return !found_state;
>
> I have modified this to:
>
> 257 if (!found_state) {
> 258 // Assuming the thread exists.
> 259 print_error("Could not find the 'State:' string in the
> /proc/%d/status file\n", pid);
> 260 }
> 261 fclose (fp);
> 262 return false;
>
> Thank you,
> Jini.
>
> >
> > Thanks!
> > Jc
> >
> > On Tue, Dec 11, 2018 at 9:30 AM Jini George
> <jini.geo...@oracle.com <mailto:jini.geo...@oracle.com>
<mailto:jini.geo...@oracle.com <mailto:jini.geo...@oracle.com>>
> > <mailto:jini.geo...@oracle.com
<mailto:jini.geo...@oracle.com> <mailto:jini.geo...@oracle.com
<mailto:jini.geo...@oracle.com>>>>
> wrote:
> >
> > Hello !
> >
> > Requesting reviews for:
> >
> > https://bugs.openjdk.java.net/browse/JDK-8202884
> > Webrev:
> http://cr.openjdk.java.net/~jgeorge/8202884/webrev.00/index.html
> >
> > Details:
> > For attaching to the threads in a process, we first go
ahead
> and do a
> > ptrace attach to the main thread. Later, we use the
libthread_db
> > library
> > (or, in the case of being within a container, iterate
through the
> > /proc/<pid>/task files) to discover the threads of the
> process, and add
> > them to the threads list (within SA) for this process.
Once,
> we have
> > discovered all the threads and added these to the list of
> threads, we
> > then invoke ptrace attach individually on all these
threads to
> > attach to
> > these. When we deal with an application where the
threads are
> exiting
> > continuously, some of these threads might not exist by the
> time we try
> > to ptrace attach to these threads. The proposed fix
includes the
> > following modifications to solve this.
> > 1. Check the state of the threads in the thread_db
> callback routine,
> > and skip if the state of the thread is TD_THR_UNKNOWN or
> TD_THR_ZOMBIE.
> > SA does not try to ptrace attach to these threads and does
> not include
> > these threads in the threads list.
> > 2. While ptrace attaching to the thread, if
> ptrace(PTRACE_ATTACH,
> > ...)
> > fails with either ESCRH or EPERM, check the state of the
> thread by
> > checking if the /proc/<pid>/status file corresponding
to that
> thread
> > exists and if so, reading in the 'State:' line of that
file. Skip
> > attaching to this thread and delete this thread from
the SA
> list of
> > threads, if the thread is dead (State: X) or is a zombie
> (State: Z).
> > From the /proc man page, "Current state of the
process. One
> of "R
> > (running)", "S (sleeping)", "D (disk sleep)", "T
(stopped)", "T
> > (tracing
> > stop)", "Z (zombie)", or "X (dead)"."
> > 3. If waitpid() on the thread is a failure, again skip
> this thread
> > (delete this from SA's list of threads) instead of bailing
> out if the
> > thread has exited or terminated.
> >
> > Testing:
> > 1. Tested by attaching and detaching multiple times to
a test
> program
> > spawning numerous short lived threads.
> > 2. The SA tests (under
test/hotspot/jtreg/serviceability/sa)
> passed
> > with
> > 100 repeats on Mach5.
> > 3. No new failures and no occurrences of JDK-8202884 seen
> with testing
> > the SA tests (tiers 1 to 5) on Mach5.
> >
> > More details in the bug comments section.
> >
> > Thank you,
> > Jini.
> >
> >
> >
> > --
> >
> > Thanks,
> > Jc
>
>
>
> --
>
> Thanks,
> Jc
--
Thanks,
Jc
