RFR: 8197408: Bad pointer comparison and small cleanup in os_linux.cpp
Robbin Ehn
robbin.ehn at oracle.com
Mon Feb 19 13:03:51 UTC 2018
Hi Bob,
On 02/15/2018 04:50 PM, Bob Vandette wrote:
> The changes look ok to me.
>
Thanks!
> I would have preferred that you kept the original logic embedded in the
> higher level functions rather than adding additional static functions. We’re hoping
> to back port this capability to JDK 8 and it just makes the merges more error prone.
Here I moved the logic back:
http://cr.openjdk.java.net/~rehn/8197408/v3/inc/
http://cr.openjdk.java.net/~rehn/8197408/v3/full/
I prefer the v2 version of os_linux.cpp, stick with v3 or go back to v2?
I also added a test which just verifies we can read the cgroup's values without
failing when in a container. And if not in container verifies that we failed as
expected.
Both v2 and v3 passes this test via the in container case.
Thanks, Robbin
>
> I’m also a bit uncomfortable with freeing potentially NULL pointers in print_container_info.
> I’ve worked with too many different Linux clibs to trust that they all have the same
> behavior but it is documented on both Linux and Bsd so I guess we’re ok.
>
> Bob.
>
>
>
>> On Feb 15, 2018, at 4:37 AM, Robbin Ehn <robbin.ehn at oracle.com> wrote:
>>
>> Hi Thomas, thanks for having a look.
>>
>> On 2018-02-14 15:06, Thomas Stüfe wrote:
>>> Hi Robin,
>>> Had a short look. Note that I cannot open the issue. Link is wrong, and the link in the source.patch is wrong too. So, I just looked at the webrev.
>>
>> Sorry bug is:
>> https://bugs.openjdk.java.net/browse/JDK-8197408
>>
>> Inc here:
>> http://cr.openjdk.java.net/~rehn/8197408/v2/inc/webrev/
>> Full here:
>> http://cr.openjdk.java.net/~rehn/8197408/v2/full/webrev/
>>
>> Comments on remarks below:
>>
>>> Remarks:
>>> -> This is a matter of taste but I prefer pointers to references for output variables. Makes the intent clearer at the calling site, and that way you could get rid of the /* output */ comment.
>>
>> We had a debate about this, my opinion was that avoiding the NULL check makes it worth using a ref, but I see I'm pretty lonely in this camp so fixed.
>>
>>> -> in available_memory_container():
>>> Could we also add "using host value" to the logging in error case as you do in physical_memory_container()?
>>
>> Fixed, and tried to improve the logs.
>>
>>> -> (Not part of your patch) Can OSContainer::memory_limit_in_bytes() actually ever return "OSCONTAINER_ERROR"? I may be wrong here but:
>>> OSCONTAINER_ERROR = -2. /memory.limit_in_bytes gets returned as julong, so we have (julong)(-2). That gets compared with julong _unlimited_memory which is basically LONG_MAX, so signed long max, which should be smaller than (julong)(-2), or? So OSContainer::memory_limit_in_bytes() should always return -1 for both errors and the unlimited case.
>>
>> Manually tested this, it seems to work. The -2 gets promoted to unsigned in comparison.
>> We go from (jlong)-2 to (julong)ULONG_MAX-1 back to (jlong)-2.
>> Not obviously that it will always work. I will not touch that in this changeset.
>>
>>> -> Can we:
>>> - st->print("container_type: %s\n", p != NULL ? p : "failed");
>>> + st->print_cr("container_type: %s", p != NULL ? p : "failed");
>>> ?
>>
>> All of these use print + \n, you want me to just change this one or ?
>> I'll rather leave them alone.
>>
>>> -> char * OSContainer::container_type() - you free() that value but it is not strdup()ed.
>>
>> Thanks for seeing this, copy-paste :)
>>
>>> (Btw I do not like that some functions return strduped values, some do not. If OSContainer::container_type() wants to return a static string, its return type should be at least const char*, not char*. They even added an explicit cast to nonconst char* .)
>>
>> Changed to const.
>>
>> Thanks, Robbin
>>
>>> Kind Regards, Thomas
>>> On Wed, Feb 14, 2018 at 2:18 PM, Robbin Ehn <robbin.ehn at oracle.com <mailto:robbin.ehn at oracle.com>> wrote:
>>> Ping!
>>> /Robbin
>>> On 2018-02-08 13:35, Robbin Ehn wrote:
>>> Hi David,
>>> On 02/08/2018 01:19 PM, David Holmes wrote:
>>> On 8/02/2018 10:08 PM, Robbin Ehn wrote:
>>> Hi David,
>>> On 02/08/2018 12:43 PM, David Holmes wrote:
>>> Hi Robbin,
>>> On 8/02/2018 7:03 PM, Robbin Ehn wrote:
>>> Hi all,
>>> There is a bad pointer comparison in os_linux.cpp while looking at that
>>> You seem to be missing the fact that OSContainer::cpu_cpuset_memory_nodes() can return a pointer or an error code.
>>> This is not true for macro:
>>> GET_CONTAINER_INFO_CPTR
>>> As far I can see?
>>> Sorry - you're right. I misread current code and misremembered what happened at the initial code review - where I'm sure this "pointer versus error code" issue was also flagged.
>>> It returns:
>>> if (err != 0)
>>> return (return_type) NULL;
>>> or:
>>> return os::strdup(mems);
>>> If you know a method that returns an integer in a char*, it's broken should be fixed.
>>> I saw some if statement were missing bracket, a lot of extra scopes and complexity in the scoping.
>>> You'd better check all this with Bob Vandette as its his container support code.
>>> Not sure what you mean. It passes container tests.
>>> In what environment did you run the container tests? Most of the code you've been refactoring deals with various errors and misconfigurations that can occur.
>>> I'm sure Bob will want a chance to check the refactoring still does as he intended.
>>> On mach5 all platforms with the container test (+ hotspot_tier1) and locally.
>>> I said before, regarding containers, all Linux have cgroups configured so this logic always thinks we are in a container and does this logging and calculation.
>>> But no there is no tests for miss-configuration that I found.
>>> Added Bob!
>>> Thanks, Robbin
>>> Cheers,
>>> David
>>> -----
>>> Thanks, Robbin
>>> Cheers,
>>> David
>>> Webrev:
>>> http://cr.openjdk.java.net/~rehn/8197408/webrev/ <http://cr.openjdk.java.net/~rehn/8197408/webrev/>
>>> Bug:
>>> http://cr.openjdk.java.net/~rehn/8197408/webrev/ <http://cr.openjdk.java.net/~rehn/8197408/webrev/>
>>> Thanks, Robbin
>
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