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Message-ID: <48546934-5ccd-0b1e-bf2b-306133101c6b@landley.net>
Date: Wed, 27 Jul 2022 01:34:41 -0500
From: Rob Landley <rob@...dley.net>
To: musl@...ts.openwall.com
Subject: Re: sysconf(_SC_NPROCESSORS_CONF) broken.
On 7/27/22 01:28, Rob Landley wrote:
> NPROCESSORS_CONF is supposed to show total processors, NPROCESSORS_ONLN shows
> available processors using the tasket mask sched_getaffinity()).
>
> Musl is (uniquely) using the getaffinity() version for both. Neither glibc nor
> bionic have that bug.
>
> Test: my laptop has 4 processors:
>
> $ taskset 7 nproc
> 3
> $ taskset 7 nproc --all
> 4
>
> With musl, both show 3.
P.S. According to strace, devuan's nprocs --all is reading sysfs:
openat(AT_FDCWD, "/sys/devices/system/cpu",
O_RDONLY|O_NONBLOCK|O_CLOEXEC|O_DIRECTORY) = 3
fstat(3, {st_mode=S_IFDIR|0755, st_size=0, ...}) = 0
getdents64(3, /* 22 entries */, 32768) = 656
getdents64(3, /* 0 entries */, 32768) = 0
At a guess, counting the cpu[0-9]* entries? I looked at bionic's source and it
had a comment that x86 can use /proc/cpuinfo but arm only shows "available"
processors there, not total processors...
Rob
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