numa_helper: don't break is_numa() with TCONF

From: "Cyril Hrubis" <[email protected]>
To: "Jan Stancek" <[email protected]>
Cc: [email protected]
Sent: Monday, 22 February, 2016 2:25:22 PM
Subject: Re: [LTP] [PATCH] numa_helper: don't break is_numa() with TCONF

Hi!

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And the same for is_numa(), it calls tst_brkm(TBROK | TERRNO, ...) in case that get_allowed_nodes_arr() returned non-zero.

If get_allowed_nodes_arr() returned non-zero because of get_mempolicy, that means get_mempolicy is implemented but failed. I think that justifies TBROK.

Now I'm confused. You said that the syscall can exit -1 and ENOSYS.

In that case the filter_nodemask_mem() returns -2 which is propagated from get_allowed_nodes_arr() to is_numa() where the test ends with TBROK rather than with TCONF.

Or did I miss something?

--
Cyril Hrubis
[email protected]

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Now I'm confused. You said that the syscall can exit -1 and ENOSYS.

Correct, get_mempolicy is not implemented on aarch64.

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In that case the filter_nodemask_mem() returns -2 which is propagated from get_allowed_nodes_arr() to is_numa() where the test ends with TBROK rather than with TCONF.

It won't return -2 for ENOSYS, because of this line:
+ if (ret < 0 && errno != ENOSYS)

                 return -2;

Quoted 1 line

Or did I miss something?

I didn't make it clear in commit message that patch now silently ignores ENOSYS from get_mempolicy. In this case get_allowed_nodes should return success, but returned node set should be empty (I'll double check that this is the case on aarch64).

From: "Cyril Hrubis" <[email protected]>
To: "Jan Stancek" <[email protected]>
Cc: [email protected]
Sent: Monday, 22 February, 2016 3:26:33 PM
Subject: Re: [LTP] [PATCH] numa_helper: don't break is_numa() with TCONF

Hi!

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Quoted 1 line

Now I'm confused. You said that the syscall can exit -1 and ENOSYS.

Correct, get_mempolicy is not implemented on aarch64.

Quoted 4 lines

In that case the filter_nodemask_mem() returns -2 which is propagated from
get_allowed_nodes_arr() to is_numa() where the test ends with TBROK rather than with TCONF.

It won't return -2 for ENOSYS, because of this line:
+ if (ret < 0 && errno != ENOSYS)

                 return -2;

Quoted 8 lines

Quoted 1 line

Or did I miss something?

I didn't make it clear in commit message that patch now silently ignores ENOSYS
from get_mempolicy. In this case get_allowed_nodes should return success, but
returned node set should be empty (I'll double check that this is the case on aarch64).

Ah right I somehow missed that (I blame it on not enough coffe in bloodstream). So is_numa() returns 0 in that case, which is fine.

If node set is empty the get_allowed_nodes() will fail since the num_nodes will end up set to 0 and get_allowed_nodes() will return with -3 and errno EINVAL since we cannot set the requested node. And looks like at least oom04 and oom05 call TBROK if there isn't one allowed node.

--
Cyril Hrubis
[email protected]