linux-kernel - Re: [PATCH v4 0/3] vfs: Define new syscall umask2 [formerly getumask]

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Date:	Wed, 13 Apr 2016 12:37:42 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	"Richard W.M. Jones" <rjones@...hat.com>,
	linux-kernel@...r.kernel.org
Cc:	tglx@...utronix.de, mingo@...hat.com, akpm@...ux-foundation.org,
	luto@...nel.org, viro@...iv.linux.org.uk,
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	paulmck@...ux.vnet.ibm.com, aarcange@...hat.com,
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	iulia.manda21@...il.com, dave.hansen@...ux.intel.com,
	mguzik@...hat.com, adobriyan@...il.com, dave@...olabs.net,
	linux-api@...r.kernel.org, gorcunov@...il.com, fw@...eb.enyo.de,
	walters@...bum.org
Subject: Re: [PATCH v4 0/3] vfs: Define new syscall umask2 [formerly getumask]

On 04/13/16 12:05, Richard W.M. Jones wrote:
> v3 -> v4:
>
>   - Rename the syscall: getumask becomes umask2.
>
>   - Add flags parameter, with one flag (UMASK_GET_MASK).
>
>   - Expand the rationale for this change in the first commit message.
>
>
> It's not possible to read the process umask without also modifying it,
> which is what umask(2) does.  A library cannot read umask safely,
> especially if the main program might be multithreaded.
>

I wouldn't say "if"; that is the case when it matters.

I have to say I'm skeptic to the need for umask2() as opposed to 
getumask().  I would also like to be able to get the umask of another 
process, which would argue for adding it to /proc anyway.

	-hpa