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From: Elizabeth Figura <zfigura@codeweavers.com>
To: Peter Zijlstra <peterz@infradead.org>, wine-devel@winehq.org
Cc: Arnd Bergmann <arnd@arndb.de>,
 Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
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 =?ISO-8859-1?Q?Andr=E9?= Almeida <andrealmeid@igalia.com>,
 Wolfram Sang <wsa@kernel.org>, Andy Lutomirski <luto@kernel.org>,
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 Will Deacon <will@kernel.org>, Waiman Long <longman@redhat.com>,
 Boqun Feng <boqun.feng@gmail.com>, Elizabeth Figura <zfigura@codeweavers.com>
Subject: Re: [PATCH v4 00/30] NT synchronization primitive driver
Date: Wed, 15 May 2024 18:32:26 -0500
Message-ID: <2322852.ElGaqSPkdT@watership>
In-Reply-To: <1790266.VLH7GnMWUR@camazotz>
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 <20240417100132.GK30852@noisy.programming.kicks-ass.net>
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On Wednesday, April 17, 2024 3:02:13=E2=80=AFPM CDT Elizabeth Figura wrote:
> > > Except for the "unowned" semantics of zero, the actual value of the
> > > owner identifier is not interpreted by the ntsync driver at all. The
> > > intended use is to store a thread identifier; however, the ntsync
> > > driver does not actually validate that a calling thread provides
> > > consistent or unique identifiers.
> >=20
> > Why not verify it? Seems simple enough to put in a TID check, esp. if NT
> > mandates the same.
>=20
> I mostly figured it'd be simplest to leave the driver completely
> agnostic, but I don't think there's any reason we can't use the real
> TID for most calls.

While trying to implement this I did realize a reason: if a Linux thread di=
es=20
and a new Wine thread is created which happens to have the same Linux TID=20
*before* Wine notices the thread death, that thread's TID will be conflated=
=20
with the thread that died. I don't think we can guarantee that we notice=20
thread death before we notice a request to create a new Wine thread.

Using Wine-managed TIDs avoids this by virtue of ensuring that a Wine TID i=
s=20
not reused until the associated Wine thread has been cleaned up.