Re: [Qemu-devel] [PATCH] win32: replace custom mutex and condition variable with native primitives

[Cornelia Huck <cornelia.huck@de.ibm.com>]

On Fri, 24 Mar 2017 15:01:41 -0700
Andrew Baumann <Andrew.Baumann@microsoft.com> wrote:

> From: Andrey Shedel <ashedel@microsoft.com>
> 
> The multithreaded TCG implementation exposed deadlocks in the win32
> condition variables: as implemented, qemu_cond_broadcast waited on
> receivers, whereas the pthreads API it was intended to emulate does
> not. This was causing a deadlock because broadcast was called while
> holding the IO lock, as well as all possible waiters blocked on the
> same lock.
> 
> This patch replaces all the custom synchronisation code for mutexes
> and condition variables with native Windows primitives (SRWlocks and
> condition variables) with the same semantics as their POSIX
> equivalents. To enable that, it requires a Windows Vista or newer host
> OS.
> 
> [AB: edited commit message]
> Signed-off-by: Andrew Baumann <Andrew.Baumann@microsoft.com>
> ---
> The major implication of this patch is that it drops support for
> pre-Vista versions of Windows. However, those OSes are past their end
> of life, and other OSS projects have dropped support. e.g.; the last
> Cygwin release supporting XP was in Jun 2016. It doesn't seem like a
> good tradeoff to invest effort in fixing broken code needed to support
> them, so hopefully this isn't too controversial.

Just a quick question:

I noticed that this breaks builds on an old fc20-based installation I
run some mingw cross builds on (getting an undefined reference to
`_imp__TryAcquireSRWLockExclusive@4'). I should probably take that as a
trigger to update that installation ;), but wanted to confirm that this
is expected.