[libvirt] [PATCH 4/7] Fix potential deadlock across fork() in QEMU driver

[Cole Robinson]

On 07/23/2013 11:03 AM, Eric Blake wrote:
> From: "Daniel P. Berrange" <berrange at redhat.com>
> 
> https://bugzilla.redhat.com/show_bug.cgi?id=964358
> 
> The hook scripts used by virCommand must be careful wrt
> accessing any mutexes that may have been held by other
> threads in the parent process. With the recent refactoring
> there are 2 potential flaws lurking, which will become real
> deadlock bugs once the global QEMU driver lock is removed.
> 
> Remove use of the QEMU driver lock from the hook function
> by passing in the 'virQEMUDriverConfigPtr' instance directly.
> 
> Add functions to the virSecurityManager to be invoked before
> and after fork, to ensure the mutex is held by the current
> thread. This allows it to be safely used in the hook script
> in the child process.
> 
> Signed-off-by: Daniel P. Berrange <berrange at redhat.com>
> (cherry picked from commit 61b52d2e3813cc8c9ff3ab67f232bd0c65f7318d)
> 
> Conflicts:
> 	src/libvirt_private.syms - context
> 	src/qemu/qemu_process.c - no backport of qemud_driver struct rename
> 	src/security/security_manager.c - no backport of making the security driver self-locking; just expose the interface

ACK

- Cole