Re: [PATCH] proc: revert /proc/<pid>/maps [stack:TID] annotation
From: Siddhesh Poyarekar
Date: Tue Jan 19 2016 - 22:17:50 EST
On 20 January 2016 at 03:44, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:
> Any thoughts on the obvious back-compatibility concerns? ie, why did
> Siddhesh implement this in the first place? My bad for not ensuring
> that the changelog told us this.
> https://lkml.org/lkml/2012/1/14/25 has more info:
> : Memory mmaped by glibc for a thread stack currently shows up as a
> : simple anonymous map, which makes it difficult to differentiate between
> : memory usage of the thread on stack and other dynamic allocation.
> : Since glibc already uses MAP_STACK to request this mapping, the
> : attached patch uses this flag to add additional VM_STACK_FLAGS to the
> : resulting vma so that the mapping is treated as a stack and not any
> : regular anonymous mapping. Also, one may use vm_flags to decide if a
> : vma is a stack.
> But even that doesn't really tell us what the actual *value* of the
> patch is to end-users.
The end users needed a way to identify thread stacks programmatically
and there wasn't a way to do that. I'm afraid I no longer remember
(or have access to the resources that would aid my memory since I
changed employers) the details of their requirement. However, I did
do this on my own time because I thought it was an interesting project
for me and nobody really gave any feedback then as to its utility, so
as far as I am concerned you could roll back the main thread maps
information since the information is available in the thread-specific