ERL-1012: cpu_sup:util() always return 100.0

[OTP-Maintainer]

Original reporter: zhouzb
Affected version: OTP-21.0
Fixed in version: OTP-22.1
Component: os_mon
Migrated from: https://bugs.erlang.org/browse/ERL-1012

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I am using the [Alpine Erlang Docker Image|https://github.com/erlang/docker-erlang-otp/tree/3765be4573e249004e48a5de9c94127a214b1e6f/21/alpine]. I encountered the problem mentioned in the title, the root cause could be "%Lu" is not supported by Alpine OS.
I fix it by replaceing "%Lu" with "%llu" at in cpu_sup.c:362

{code:c}
    sscanf(buffer, "cpu%u %Lu %Lu %Lu %Lu %Lu %Lu %Lu %Lu",
	&(cpu->id),
	&(cpu->user),
	&(cpu->nice_user),
	&(cpu->kernel),
	&(cpu->idle),
	&(cpu->io_wait),
	&(cpu->hard_irq),
	&(cpu->soft_irq),
	&(cpu->steal));

    return cpu;
{code}

[OTP-Maintainer]

mikael pettersson said:

{{%L}} is a non-standard feature, supported by GNU libc but not e.g. musl.  {{%ll}} is appropriate here (the code is ifdef linux so no need to switch to int64_t and SCNu64).

[OTP-Maintainer]

zhouzb said:

Could you tell me something about your plan, like when you're going to fix it?

[OTP-Maintainer]

lukas said:

[~Zhouzb] I've opened a PR with the fix here: https://github.com/erlang/otp/pull/2340

In the future, if a fix is important to you to get fixed it is quicker to just submit a pr yourself.

Thanks for the bug report! The fix should be part of the next maintenance release.

[OTP-Maintainer]

zhouzb said:

Thank you very match!