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Re: [PATCH] Async signal safe TLS accesses
- From: "Carlos O'Donell" <carlos at redhat dot com>
- To: Rich Felker <dalias at aerifal dot cx>, OndÅej BÃlka <neleai at seznam dot cz>
- Cc: Alexandre Oliva <aoliva at redhat dot com>, Paul Pluzhnikov <ppluzhnikov at google dot com>, Andrew Hunter <ahh at google dot com>, "Joseph S. Myers" <joseph at codesourcery dot com>, GLIBC Devel <libc-alpha at sourceware dot org>
- Date: Thu, 28 Nov 2013 23:26:03 -0500
- Subject: Re: [PATCH] Async signal safe TLS accesses
- Authentication-results: sourceware.org; auth=none
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On 11/28/2013 11:01 PM, Rich Felker wrote:
> On Fri, Nov 29, 2013 at 04:55:48AM +0100, OndÅej BÃlka wrote:
>> A proper solution would be make generic malloc async-signal safe. It is
>> question of what is acceptable overhead. I can make a wrapper over any
>> allocator that does that at cost of two tls access. You would pay a mmap
>> overhead only when you are in signal where we do not care about
> Not a solution as long as glibc officially supports applications
> replacing malloc.
The loader could access the implementation's malloc via GLIBC_PRIVATE
I'm against this because any sufficiently complex and performant
implementation of malloc will be difficult to audit for AS-safety.
In the end AS-safety may even limit your flexibility, but I don't
discount the possibility of writing the allocator such that it performs
A small signal-safe allocator as proposed by Google is the easiest way
to get the job done. We can always fix this later.