RFR (M/L): 8131168: Refactor ProcessHandleImpl_*.c and add implememtation for AIX
Stuart Marks
stuart.marks at oracle.com
Tue Aug 11 22:19:34 UTC 2015
.. and of course right after I sent my previous message, I ran across something
worth noting.
The proposed spec for commandLine() says,
* If {@link #command command()} and {@link #arguments arguments()} return non-null
* optionals,
The preferred term is "non-empty" instead of non-null. This is kind of nitpicky
but in fact command() and arguments() should NEVER return an actual null; they
should always return an Optional that is either empty or that has a value. So I
think this is important to change lest someone be misled into writing
if (info.command() == null && info.arguments() == null) ...
Thanks,
s'marks
On 8/11/15 3:07 PM, Stuart Marks wrote:
> Hi Volker,
>
> I looked at the proposed specification of commandLine() after the most recent
> round of reviews (which is 8131168.v6 I believe) and it looks fine to me. It
> expresses the intent pretty well. Oh, and the name "commandLine" is fine and it
> fits well with the names of the other methods.
>
> Thanks,
>
> s'marks
>
> On 8/11/15 8:52 AM, Volker Simonis wrote:
>> On Tue, Aug 11, 2015 at 5:08 PM, Roger Riggs <Roger.Riggs at oracle.com> wrote:
>>> Hi Volker,
>>>
>>> Thanks for checking into the details of the OS X sysctl. I'm fine with the
>>> current implementation.
>>>
>>> The rest of the updates and the additional tests look fine also.
>>>
>>
>> Phew! I was already afraid I would have to switch to double-digit
>> versions for my webrevs :)
>>
>>> But I need to check on the CCC status.
>>>
>>
>> OK, please let me know once it is ready/approved.
>>
>> Regards,
>> Volker
>>
>>> Thanks, Roger
>>>
>>>
>>>
>>>
>>> On 8/10/15 10:13 AM, Volker Simonis wrote:
>>>
>>> On Fri, Aug 7, 2015 at 8:54 PM, Roger Riggs <Roger.Riggs at oracle.com> wrote:
>>>
>>> Hi Volker,
>>>
>>> 1) ProcessHandle.java:243
>>>
>>> For the definition of the new commandLine method I would:
>>>
>>> - Use @link instead of @code for references to commands() and arguments()
>>> for easy navigation
>>>
>>> - @implNote[1] should I think be changed to @apiNote:
>>> the text describes not the JDK implementation but is information about the
>>> information returned and is use to the application developer, not the JDK
>>> implementation.
>>>
>>> - The specific references to Linux implementation command line length
>>> parameters seems out of place
>>> and should be omitted.
>>>
>>> /**
>>> * Returns the command line of the process.
>>> * <p>
>>> * If {@link #command command()} and {@link #arguments arguments()}
>>> return non-null
>>> * optionals, this is simply a convenience method which concatenates
>>> * the values of the two functions separated by spaces. Otherwise it
>>> will return a
>>> * best-effort, platform dependent representation of the command
>>> line.
>>> *
>>> * @apiNote Note that the returned executable pathname and the
>>> * arguments may be truncated on some platforms due to
>>> system
>>> * limitations.
>>> * <p>
>>> * The executable pathname may contain only the
>>> * name of the executable without the full path
>>> information.
>>> * It is undecideable whether white space separates
>>> different
>>> * arguments or is part of a single argument.
>>> *
>>> * @return an {@code Optional<String>} of the command line
>>> * of the process
>>> */
>>> public Optional<String> commandLine();
>>>
>>>
>>> ProcessHandle.java:252: in arguments() method - @apiNote is a better fit for
>>> the note
>>>
>>> ProcessHandleImpl_macosx.c:276: - indentation +4
>>>
>>> Thanks for the correction. I've taken your wording you suggested.
>>>
>>> 2) ProcessHandleImpl_macosx.c:192:
>>> if (errno != EINVAL) ... There was previously this test, I'm concerned
>>> that if the pid is invalid,
>>> it will now throw a RuntimeException instead of returning -1.
>>> I recall a discussion from May that recommended testing for EINVAL.
>>> The sysctl in getCmdlineAndUserInfo also does not throw if errno !=
>>> EINVAL, so the usage
>>> is not consistent (probably my coding) but needs investigation.
>>>
>>> Not sure about this one and couldn't find any previous discussion
>>> about the topic.
>>>
>>> But, according to the sysctl man-page, EINVAL is only returned if:
>>> - The name array is less than two or greater than CTL_MAXNAME.
>>> - A non-null newp is given and its specified length in newlen is too
>>> large or too small.
>>>
>>> The first case can not happen because we always statically allocate
>>> arrays of the correct size.
>>> The second case can not happen as well, because we always have 'newp ==
>>> NULL'.
>>>
>>> So according to this information I don't see any reason why we should
>>> check for EINVAL. I think the right solution is to check for 'oldlenp
>>>
>>> 0' which we already do. By the way, this is also the check applied
>>>
>>> by the psutils (see the implementation of 'get_kinfo_proc()' in [1]).
>>>
>>> So I wnated to also removed the last check for EINVAL in
>>> getCmdlineAndUserInfo(). But for some reason, that seems to be really
>>> necessary. Without it, we will get a RuntinmeException if we call
>>> sysinfo for pid==0 for example. Further research showed that the
>>> kernel seems to really return EINVAL for KERN_PROCARGS2 (see function
>>> sysctl_procargsx() in [2]). But KERN_PROCARGS2 isn't specified as a
>>> supported constant in the sysctl man-page, so the information there is
>>> still valid :)
>>>
>>> On the other hand, I found that the psutils alo handles EINVAL only
>>> for KERN_PROCARGS2 (see get_arg_list() in [1]).
>>>
>>> So to cut a long story short, I think the current implementation is
>>> safe as it is now!
>>>
>>> [1] http://psutil.googlecode.com/svn/trunk/psutil/arch/osx/process_info.c
>>> [2]
>>> http://www.opensource.apple.com/source/xnu/xnu-1699.24.23/bsd/kern/kern_sysctl.c
>>>
>>> 3) ProcessHandleImpl_solaris.c can do without the includes:
>>> #include "jni_util.h"
>>> #include "java_lang_ProcessHandleImpl.h"
>>> #include "java_lang_ProcessHandleImpl_Info.h"
>>>
>>> #include <stdio.h>
>>>
>>> 4) Ditto ProcessHandleImpl_aix.c
>>>
>>> Thanks, fixed.
>>>
>>> 5) ProcessHandleImpl_unix.c: 618: typo "fuctions" -> "functions"
>>>
>>> Fixed.
>>>
>>> 6) ProcessHandleImpl_unix.c:463: Would it be worthwhile to put
>>> sysconf(_SC_GETPW_R_SIZE_MAX) in a static?
>>>
>>> Good point! While doing this I realized that 'clock_ticks_per_second'
>>> is only used on Linux. So I moved the declaration of
>>> 'clock_ticks_per_second' from ProcessHandleImpl_unix.hpp to
>>> ProcessHandleImpl_linux.cpp and its initialization to os_initNative()
>>> in the same file.
>>>
>>> I also declare a new static 'getpw_buf_size' in
>>> ProcessHandleImpl_unix.cpp and initialize it in
>>> Java_java_lang_ProcessHandleImpl_initNative() in the same file.
>>>
>>> 7) OnExitTest.java: exits without an error, just output in the log; it would
>>> escape attention.
>>> The code respects the timeout setting.
>>> Suggest removing the 'return' @133; the test will produce some errors
>>> and when debugging
>>> the note will be in the log.
>>>
>>> Done.
>>>
>>> 8) ProcessHandleImpl_unix.h:58 - update the comment to include 0 as a valid
>>> parent pid.
>>>
>>> Fixed.
>>>
>>> Looks pretty good,
>>> Thanks, Roger
>>>
>>> Thanks:)
>>>
>>> I've also added two rudimentary tests for the new commandLine()
>>> function to InfoTest.test2():
>>>
>>> - if both, 'command()' and 'arguments()' are available, I check that
>>> 'commandLine()' starts with 'command()' and contains all the arguments
>>> from 'arguments()'.
>>>
>>> - otherwise, if 'commandLine()' is available, I check that it at
>>> least contains 'java'. And as long as it is big enough it should also
>>> contain the corresponding arguments.
>>>
>>> The two new tests have been verified to pass on Windows, Linux, MacOS
>>> X, Solaris and AIX.
>>>
>>> The new version can be found here:
>>>
>>> http://cr.openjdk.java.net/~simonis/webrevs/2015/8131168.v6/
>>>
>>> Regards,
>>> Volker
>>>
>>>
>>> [1] http://openjdk.java.net/jeps/8068562 - JEP draft: javadoc tags to
>>> distinguish API, implementation, specification, and notes
>>>
>>>
>>> On 8/5/2015 3:56 PM, Volker Simonis wrote:
>>>
>>> Hi,
>>>
>>> so here's the webrev which implements the new Info.commandLine()
>>> method (I chose 'commandLine() ' instead of 'cmdline()' or
>>> 'commandline()' because the other getters are camel case as well):
>>>
>>> http://cr.openjdk.java.net/~simonis/webrevs/2015/8131168.v4/
>>>
>>> From the JavaDoc of the new method:
>>>
>>> * If {@code command()} and {@code arguments()} return non-null
>>> * optionals, this is simply a convenience method which concatenates
>>> * the values of the two functions. Otherwise it will return a
>>> * best-effort, platform dependent representation of the command line.
>>>
>>> This didn't change anything on MacOS X where there is no additional
>>> effort to get the command line.
>>>
>>> On Solaris and AIX, Info.commandLine() will always return the contents
>>> of psinfo.pr_psargs because there's no other method to get the exact
>>> arguments (i.e. Info.arguments() always returns NULL. I could
>>> therefore remove the extra handling of AIX/Solaris in the InfoTest
>>> from my initial change.
>>>
>>> On Linux, things are a little more complicated:
>>>
>>> - the initial implementation for Linux used arg[0] as 'command' if
>>> /proc/pid/exe wasn't readable. This was true for all the processes we
>>> don't own (except if we are running as root). But this information may
>>> be incomplete, because arg[0] may only contain the command without its
>>> full path. One example is 'sendmail' for which Info.command() reported
>>> "sendmail: accepting connections" but Info.arguments() was empty. This
>>> is wrong, because 'sendmail' changes its argv[] array. I have
>>> therefore disabled this behavior now that we have the 'commandLine()'
>>> method.
>>>
>>> - /proc/pid/cmdline is limited to PAGE_SIZE (normally 4096) characters
>>> on Linux. So strictly speaking, this isn't 'exact' information as well
>>> (there are plenty of complains that especially for Java programs this
>>> is not enough) and should go to 'commandLine()' instead to 'arguments'
>>> if /proc/pid/cmdline is truncated. I do check for this now.
>>>
>>> - the information in /proc/pid/cmdline can also be changed to
>>> something other than the original arguments if a program changes
>>> argv[] (which is not forbidden) but there's probably not much we can
>>> do to detect this. I've added a corresponding @implNote comment to
>>> JavaDoc of Info.arguments().
>>>
>>> - the initial implementation did not check for incomplete reads of
>>> /proc/pid/cmdline. This may be a problem on systems with PAGE_SIZE >
>>> 4096 (on Linux/ppc64 a page size of 65536 is not unusual). I'm now
>>> always reading the complete contents of /proc/pid/cmdline.
>>>
>>> - as far as I understand the current implementation, 'arguments()'
>>> returns the arguments array WITHOUT 'arg[0]' (which is the program
>>> name) but may
>>> be we should specify that more clearly in the JavaDoc of 'arguments()'.
>>>
>>> That's it. Hope you like it :)
>>>
>>> Regards,
>>> Volker
>>>
>>> On Fri, Jul 31, 2015 at 11:02 PM, Stuart Marks <stuart.marks at oracle.com>
>>> wrote:
>>>
>>> Hi Roger, Volker,
>>>
>>> Glad to see you guys are receptive to this and that it can move forward. Let
>>> me know if you'd like me to help out, for example with reviews or something.
>>>
>>> s'marks
>>>
>>>
>>> On 7/31/15 9:55 AM, Roger Riggs wrote:
>>>
>>> Hi Volker,
>>>
>>> I agree that adding an Info.commandline() method would be a good way
>>> to make the command line available and be able to describe that it is
>>> OS dependent and may be truncated.
>>> And having it assemble the command and arguments when they are available
>>> makes
>>> sense.
>>> As an API addition it will need a clear spec and I can run it through CCC
>>> so it
>>> gets
>>> another review and compatibility tests.
>>>
>>> Thanks, Roger
>>>
>>>
>>>
>>>
>>> On 7/31/2015 5:03 AM, Volker Simonis wrote:
>>>
>>> On Fri, Jul 31, 2015 at 2:51 AM, Stuart Marks <stuart.marks at oracle.com>
>>> wrote:
>>>
>>> On 7/29/15 11:36 AM, Volker Simonis wrote:
>>>
>>> !! ProcessHandleImpl_unix: 709-738: I still disagree with returning
>>> truncated or incomplete
>>> values for the executable or arguments.
>>> Can anyone be a tie-breaker (with a good rational and suggestion for
>>> how
>>> an
>>> application can use the data).
>>>
>>> As I wrote, I agree to hear other opinions here.
>>>
>>> All I want to say that this truncated data is actually what 'ps' is
>>> reporting on Solaris since decades and people seem to be happy with
>>> it. As use case I can imagine logging or monitoring (something like
>>> 'top' in Java) where this data will be just good enough.
>>>
>>> We could specially mark possibly incomplete data by extending the Info
>>> object with functions like commandIsExact() or argumentsIsPrecise().
>>> But notice that we can not statically preset these values per
>>> platform. For example on Solaris, the 'command()' would return a
>>> precise value for processes with the same uid like the VM but only
>>> inaccurate values for all other processes. The "arguments()" would be
>>> always inaccurate on Solaris/AIX.
>>>
>>> It seems like there are cases where either exact or only approximate
>>> information is available. And as you observed, you might get one or the
>>> other on the same platform, depending on the UID. It also might depend
>>> on
>>> process state; I believe that some information becomes inaccessible when
>>> the
>>> process enters the zombie state.
>>>
>>> I don't think we should simply ignore one case or the other, but I also
>>> don't think we should try to cram the different information into the
>>> same
>>> API.
>>>
>>> The current ProcessHandle.Info api has
>>>
>>> Optional<String> command()
>>> Optional<String[]> arguments()
>>>
>>> It sounds to me like Roger wants these to contain only exact
>>> information.
>>> That seems reasonable, and this probably needs to be specified more
>>> clearly
>>> to contrast with what's below.
>>>
>>> On Solaris, the psinfo_t struct has char pr_psargs[PRARGSZ] which is a
>>> single string which appears to be the concatenation of the arguments
>>> (maybe
>>> including the command name). It's also truncated to fit PRARGSZ. It
>>> doesn't
>>> make sense to me to try to return this as a String[], as the zeroth
>>> element
>>> of that array, and certainly not parsed out into "words". So maybe
>>> instead
>>> we should have a different API that returns an imprecise command line as
>>> a
>>> single string:
>>>
>>> Optional<String> cmdline()
>>>
>>> (Naming bikeshed TBS). The semantics would be that this is the process'
>>> command and arguments concatenated into a single string (thus
>>> potentially
>>> losing argument boundaries) and also possibly truncated based on
>>> platform
>>> (COUGHsolarisCOUGH) limitations. It's certainly useful for printing out
>>> in a
>>> ps, top, or Activity Monitor style application, for informational
>>> purposes.
>>>
>>> If this were implemented, then on Solaris, command() and arguments()
>>> would
>>> always return empty optionals.
>>>
>>> I'm not sure what this should be if the exact information is available.
>>> It
>>> would be inconvenient if something that just wanted to print out an
>>> approximate command line had to check several different APIs to get the
>>> information. Maybe cmdline() could assemble the information from exact
>>> data
>>> if it's is available, by concatenating the Strings from command() and
>>> arguments(), as a convenience to the caller. But I could go either way
>>> on
>>> this.
>>>
>>> Not sure this counts as a tie-breaker, but it might be a reasonable way
>>> forward.
>>>
>>> s'marks
>>>
>>> Hi Stuart,
>>>
>>> thanks a lot for your comments - I like your proposal. For me this
>>> sounds like a good compromise.
>>>
>>> @Roger: should I go and add a new field commandLine and the
>>> corresponding getter to the Info class? As Stuart proposed, the getter
>>> could check if 'command' and 'arguments' are available and assemble
>>> the command line from them. Otherwise it could use the content of the
>>> commandLine field if that is available.
>>>
>>> Regards,
>>> Volker
>>>
>>>
>>>
More information about the core-libs-dev
mailing list