Add getrlimit and setrlimit #1302

LMJW · 2020-10-03T15:19:28Z

This PR is based on the previous PR #1190, which has not been updated for a very long time.

I have fixed the segfault and compilation error of the original PR and rebased the changes to the latest master branch.

Please let me know if anything need to been changed.

asomers · 2020-10-03T16:45:32Z

You need to fix the test failures. First of all, use libc::self is unnecessary in Rust 2018. Just remove it. I don't know if that's related to the other test failures.

LMJW · 2020-10-03T23:14:27Z

Clicked the wrong button... Will fix the issues.

LMJW · 2020-10-05T00:21:51Z

Fixed the test errors. Please review. Thank you @asomers

asomers

Rather than define Resource twice for different platforms, which doesn't even handle all platform-specificities, I think you should define Resource only once, and gate each enum item with an appropriate #[cfg(...)].

I haven't reviewed the tests yet. ENOTIME.

src/sys/resource.rs

test/test.rs

LMJW · 2020-10-06T13:23:29Z

Rather than define Resource twice for different platforms, which doesn't even handle all platform-specificities, I think you should define Resource only once, and gate each enum item with an appropriate #[cfg(...)].

I haven't reviewed the tests yet. ENOTIME.

Thank you for the suggestion. But I am not sure when enum can be both #[repr(u32)] and #[repr(i32)], how could I do this. (The reason why we have both u32 and i32 is explained in one of comments above) The closest case I can think of is using something like this:

libc_enum!{
    pub enum ResourceDemo {
        #[cfg(all(target_os = "linux", target_env = "gnu"))] #[repr(u32)]
        #[cfg(any(
            target_os = "freebsd",
            target_os = "openbsd",
            target_os = "netbsd",
            target_os = "macos",
            target_os = "ios",
            target_os = "android",
            target_os = "dragonfly",
            target_os = "linux"))] #[repr(i32)]
        RLIMIT_AS,

        #[cfg(all(target_os = "linux", target_env = "gnu"))] #[repr(u32)]
        #[cfg(any(
            target_os = "freebsd",
            target_os = "openbsd",
            target_os = "netbsd",
            target_os = "macos",
            target_os = "ios",
            target_os = "android",
            target_os = "dragonfly",
            target_os = "linux"))] #[repr(i32)]
        RLIMIT_CORE,
        RLIMIT_CPU,
        RLIMIT_DATA,
        RLIMIT_FSIZE
    }
}

But this will have compile error for linux-musl series toolchain as both cfg will be compiled thus causing the compile error. The idea I have came out is using cfg_if, but if there is better ways to do this. I am happy to adopt. Thank you very much.

asomers · 2020-10-08T02:57:04Z

Thank you for the suggestion. But I am not sure when enum can be both #[repr(u32)] and #[repr(i32)], how could I do this.
You can do it like this:

#[cfg_attr(any(target_os="linux", ...), repr(u32))]
#[cfg_attr(not(any(target_os="linux", ...), repr(u32)))]

LMJW · 2020-10-09T11:01:12Z

Thanks for given me suggestions. It is very helpful for. The new PR will be pushed out shortly. However, I have few doubts about the API of the current setrlimit and getrlimit function.

The existing api for getrlimit and setrlimit is like this

pub fn getrlimit(resource: Resource) -> Result<(Option<rlim_t>, Option<rlim_t>)>;
pub fn setrlimit(resource: Resource, soft_limit: Option<rlim_t>, hard_limit: Option<rlim_t>) -> Result<()>;

My current implementation is inherit from previous implementation, which treate None as RLIM_INFINITY. However, for some os environment, like linux_gnu, use setrlimit(Resource::RLIMIT_NOFILE, Some(1024), None) will results an EPERM error whereas other os environment will treat it is okay (see build). The EPERM error is due to None converted to RLIM_INFINITY and it is bigger than the default value1048576 , causing kernel to throw EPERM error.

The question I have is: should we treat None as RLIM_INFINITY or we should treate None as not change this value. If we decide None as not change the current value, we will need to get the orginal value first, which means we will need to call getrlimit in setrlimit method.

I feel the later case is more natural for me. But it might be my personal preference.

LMJW · 2020-10-09T11:32:56Z

Also, I feel like the previous implementation does not have enough test. But I am not sure if it is necessary to test each flag(eg RLIMIT_AS, RLIMIT_CORE ...). Eventually, it is testing libc...

LMJW · 2020-10-09T12:42:58Z

Looks like the test failure is a fake failure. Can we rerun it?

install.sh: Installing to: /home/travis/.cargo/bin
gzip: stdin: not in gzip format
tar: Child returned status 1
tar: Error is not recoverable: exiting now

asomers · 2020-10-10T15:18:50Z

Thanks for given me suggestions. It is very helpful for. The new PR will be pushed out shortly. However, I have few doubts about the API of the current setrlimit and getrlimit function.

The existing api for getrlimit and setrlimit is like this
pub fn getrlimit(resource: Resource) -> Result<(Option<rlim_t>, Option<rlim_t>)>;
pub fn setrlimit(resource: Resource, soft_limit: Option<rlim_t>, hard_limit: Option<rlim_t>) -> Result<()>;
My current implementation is inherit from previous implementation, which treate None as RLIM_INFINITY. However, for some os environment, like linux_gnu, use setrlimit(Resource::RLIMIT_NOFILE, Some(1024), None) will results an EPERM error whereas other os environment will treat it is okay (see build). The EPERM error is due to None converted to RLIM_INFINITY and it is bigger than the default value1048576 , causing kernel to throw EPERM error.

The question I have is: should we treat None as RLIM_INFINITY or we should treate None as not change this value. If we decide None as not change the current value, we will need to get the orginal value first, which means we will need to call getrlimit in setrlimit method.

I feel the later case is more natural for me. But it might be my personal preference.

I agree that treating None as "no change" would be most natural. That would be similar to how chown(2) treats an owner or group of -1. HOWEVER, that is not the API that settlimit and getrlimit provide. There is no race-free way to use setrlimit to change one limit but not the other. The goal of Nix is to provide idiomatically Rusty access to libc, but nothing more. So I don't think we should try to provide an interface like chown here.

LMJW · 2020-10-12T08:30:29Z

Hi @asomers. I think I have addressed your review comments. Please let me know if you feel like further improvements.

Thank you.

src/sys/resource.rs

Nugine · 2020-10-20T11:27:46Z

https://github.com/rust-lang/libc/blob/bc30283752bae5918f40e6d63f858203c81303c7/src/unix/bsd/apple/mod.rs#L1914

pub const RLIMIT_RSS: ::c_int = RLIMIT_AS;

RLIMIT_RSS is same with RLIMIT_AS on macos and ios. It means that the two variants will conflict when targeting apple.

Is it correct to select only one of them?

LMJW · 2020-10-21T11:05:00Z

https://github.com/rust-lang/libc/blob/bc30283752bae5918f40e6d63f858203c81303c7/src/unix/bsd/apple/mod.rs#L1914
pub const RLIMIT_RSS: ::c_int = RLIMIT_AS;
RLIMIT_RSS is same with RLIMIT_AS on macos and ios. It means that the two variants will conflict when targeting apple.

Is it correct to select only one of them?

@Nugine The reason why I select one of them is because they have the same value. If I select two of them, there will be a compile error like the following:

error[E0425]: cannot find value RLIMIT_AS in module libc
--> src/sys/resource.rs:53:17
|
53 | RLIMIT_AS,
| ^^^^^^^^^
help: a constant with a similar name exists
|
53 | RLIMIT_RSS,
| ^^^^^^^^^^
help: possible candidate is found in another module, you can import it into scope
|
2 | use crate::sys::resource::Resource::RLIMIT_AS;
|
error[E0081]: discriminant value 0 already exists
--> src/macros.rs:164:26
|
164 | $entry = libc::$entry,
| ^^^^
| |
| first use of 0
| enum already has 0
|
::: src/sys/resource.rs:48:9
|
48 | / libc_enum! {
49 | | #[repr(i32)]
50 | | pub enum Resource {
51 | | /// See detail of each Resource https://man7.org/linux/man-pages/man2/getrlimit.2.html
... |
103 | | }
104 | | }
| |_________- in this macro invocation
error: aborting due to 2 previous errors

LMJW · 2020-11-15T21:33:32Z

@asomers Do you have any further suggestions on the improvement?

Nugine · 2021-07-26T06:01:22Z

Eight months have passed. Is there any progress?
(It is the 3rd pull request for setrlimit)

LMJW · 2021-07-26T23:17:23Z

I am happy to keep work on it. Just needs more inputs on the changes

asomers · 2021-07-29T01:26:24Z

src/sys/resource.rs

+    /// earier reference (non-exhaustive).
+    ///
+    /// * [Linux](https://man7.org/linux/man-pages/man2/getrlimit.2.html)
+    /// * [freeBSD](https://www.freebsd.org/cgi/man.cgi?query=setrlimit)


The preferred spelling is "FreeBSD" (note the capital F)

Thanks for the comments. Corrected :)

asomers · 2021-07-29T01:27:38Z

src/sys/resource.rs

+        RLIMIT_NOFILE,
+        RLIMIT_STACK,
+
+        // platform specific


Why is this comment here? It seems like it should apply to every entry that has a #[cfg(...)]. But #[cfg(...)] is self-explanatory. Better just to leave it out.

asomers · 2021-07-29T01:30:49Z

src/sys/resource.rs

+/// [`Resource`]: enum.Resource.html
+///
+/// Note: `setrlimit` provides a safe wrapper to libc's `setrlimit`. For the
+/// platform that are not compatible, try using `prlimit` to set rlimit.


Is this comment obsolete now? prlimit is no longer included in the PR.

Updated the obsolete comments.

asomers · 2021-07-29T01:33:33Z

test/test_resource.rs

+pub fn test_resource_limits_nofile() {
+    let (soft_limit, hard_limit) = getrlimit(Resource::RLIMIT_NOFILE).unwrap();
+
+    // make sure the soft limit and hard limit are not equal


What ensures that the soft limit is not equal to the hard limit?

This is actually obsolete comments from the very early version of the test, see LMJW@4f8b468

For this particular test, I believe we don't need to have soft limit to equal to hard limit

LMJW · 2021-07-31T15:41:00Z

Hi @asomers. I have made some updates. Please let me know if you have any concerns. Thanks

asomers

Ok, it looks good. Just add a CHANGELOG entry and you'll be done.

@kpcyrd

This work is a continutation on previou contribution by @kpcyrd and @j1ah0ng.

LMJW · 2021-08-01T00:40:26Z

Hi @asomers. I have updated the CHANGELOG. Thanks for reviewing the pull request :)

asomers

bors r+

bors · 2021-08-01T00:57:38Z

yihuaf · 2021-08-02T06:18:59Z

When would the next release be that includes this change? Thanks.

asomers mentioned this pull request Oct 3, 2020

Add getrlimit(2) and setrlimit(2) #1190

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Add getrlimit(2) #878

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utam0k mentioned this pull request Jul 29, 2021

Refactor clone(2) child stack creation. youki-dev/youki#167

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Replace libc::getrlimit with nix wrapper youki-dev/youki#168

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LMJW force-pushed the add_rlimit branch from 2583ba1 to 6f8a421 Compare July 29, 2021 14:47

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Add getrlimit and setrlimit

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This work is a continutation on previou contribution by @kpcyrd and @j1ah0ng.

LMJW force-pushed the add_rlimit branch from daa86d7 to cd004aa Compare August 1, 2021 00:23

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rtzoeller mentioned this pull request Nov 19, 2021

Add getrlimit(2) and setrlimit(2) #879

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Arnavion mentioned this pull request Feb 24, 2022

nix::sys::resource::getrlimit doesn't actually return None #1666

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Add getrlimit and setrlimit #1302

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Add getrlimit and setrlimit #1302

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