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Subject: Re: [alpine-aports] [PATCH] testing/mongodb: fix bug #5117 where mongo fails at start
From: Marc Vertes <marc.vertes@ugrid.net>
In-Reply-To: <20160223175029.23bcadb2@vostro>
Date: Tue, 23 Feb 2016 17:10:44 +0100
Cc: alpine-aports@lists.alpinelinux.org
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Message-Id: <339A4F58-917F-455E-9B0E-E1E5A5902ADE@ugrid.net>
References: <1456083383-9196-1-git-send-email-marc.vertes@ugrid.net> <20160223150743.33e55efa@vostro.util.wtbts.net> <9D775D86-8A4D-49ED-8512-EBD572ECF6D6@ugrid.net> <20160223170446.483be803@vostro.util.wtbts.net> <E7A49593-05F0-4188-921C-7A4B1868D4FC@ugrid.net> <20160223175029.23bcadb2@vostro>
To: Timo Teras <timo.teras@iki.fi>


> Le 23 f=C3=A9vr. 2016 =C3=A0 16:50, Timo Teras <timo.teras@iki.fi> a =
=C3=A9crit :
>=20
> On Tue, 23 Feb 2016 16:35:58 +0100
> Marc Vertes <marc.vertes@ugrid.net> wrote:
>=20
>> No success. I think that the base address returned by
>> pthread_attr_getstack(&attr, &base, &size) is the problem. Increasing
>> the size (like with getrlimit) doesn't change the test in
>> StackLocator.available() which triggers abort: it checks the
>> available space against this base address (&localaddr - base > =
quota).
>>=20
>> Changing size does nothing.
>>=20
>> I also noticed that pthread_getattr_np and pthread_attr_getstack
>> where not performed from the main thread (gettid !=3D getpid)
>=20
> Right. ulimit should be used only for main thread. Not the created
> threads with libc allocated stack. That needs a fix.
>=20
> pthread_attr_getstack should return the lowest addressable byte of the
> stack. So indeed, if we change the size, we need to adjust base
> accordingly on system with downward growing stack. Something like:
>=20
> --- =
mongodb-src-r3.2.1.orig/src/mongo/platform/stack_locator_pthread_getattr_n=
p.cpp
> +++ =
mongodb-src-r3.2.1/src/mongo/platform/stack_locator_pthread_getattr_np.cpp=

> @@ -31,6 +31,7 @@
> #include "mongo/platform/stack_locator.h"
>=20
> #include <pthread.h>
> +#include <sys/resource.h>
>=20
> #include "mongo/util/assert_util.h"
> #include "mongo/util/scopeguard.h"
> @@ -52,6 +53,13 @@
>     invariant(result =3D=3D 0);
>     invariant(base !=3D nullptr);
>     invariant(size !=3D 0);
> +
> +    struct rlimit rl;
> +
> +    base +=3D size;
> +    invariant(getrlimit(RLIMIT_STACK, &rl) =3D=3D 0);
> +    size =3D rl.rlim_cur ? : 2 * 1024 * 1024;
> +    base -=3D size;
>=20
>     // TODO: Assumes a downward growing stack. Note here that
>     // getstack returns the stack *base*, being the bottom of the
>=20

This one works!
But I'm afraid of possible stack overlap between threads if it is run =
not from main thread. Is it your concern too ?

Marc=


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