> If both threads tried to upgrade, you would have a deadlock.

But how is it possible? isn't the upgrade operation atomic?

if the 2 threads try to upgrade, one will succeed and the other one will block until the first thread will unlock.

On Thu, Mar 27, 2014 at 5:39 PM, Steven Watanabe <watanabesj@gmail.com> wrote:

AMDG

On 03/27/2014 01:21 AM, Elad Moshe wrote:
> Hi,
> this is my first post here so please bare with me :) .
> I recently used upgrade_lock to try access a shared resource from 2
> different threads.
> I noticed that once the first thread acquired its upgrade_lock the second
> thread was blacked
> until the first thread unlock it.
> can someone please explain me the logic behind this behavior?
> isn't an upgrade lock just a shared_lock that can be upgraded to
> unique_lock?
> why not let both threads acquire it just like shared_lock until, and if,
> they decide to upgrade it to unique_lock?
>

If both threads tried to upgrade, you would have a deadlock.

In Christ,
Steven Watanabe

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