Date: Mon, 16 Apr 2018 17:35:13 -0400 From: Rich Felker <dalias@...ifal.cx> To: Justine Tunney <jart@...gle.com> Cc: musl@...ts.openwall.com Subject: Re: Re: musl nice() posix compliance issue On Sun, Apr 15, 2018 at 02:58:16PM -0400, Rich Felker wrote: > On Sun, Apr 15, 2018 at 10:17:37AM -0700, Justine Tunney wrote: > > According to Python 2.7 autoconf, musl's nice() function needs to do this. > > I checked latest release and HEAD. > > > > C library/kernel differences > > POSIX.1 specifies that nice() should return the new nice value. > > However, the raw Linux system call returns 0 on success. Likewise, the > > nice() wrapper function provided in glibc 2.2.3 and > > earlier returns 0 on success. > > This analysis seems correct, and from what I can tell, the SYS_nice > syscall simply isn't usable to implement nice() because it doesn't > provide the resulting nice level. So I think we have to fully drop use > of it. OTOH SYS_get/setpriority are also problematic because of > non-atomicity; we can and probably should try to patch that up by > blocking signals and taking a lock around the operation -- but I'm not > sure Linux even correctly applies the priority to all threads rather > than just the calling thread, anyway... Do you know? It doesn't, but this is a separate bug that can be worked around on its own. I'll apply a fix for the part you reported first. Rich
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