Postpone calling a given callback until unsuspend is called later.
This is different from disabling the callback, since the callback will get
invoked later if the buffer size changes between now and when we unsuspend
it.
@param the buffer that the callback is watching.
@param cb the callback we want to suspend.
Postpone calling a given callback until unsuspend is called later.
This is different from disabling the callback, since the callback will get invoked later if the buffer size changes between now and when we unsuspend it.
@param the buffer that the callback is watching. @param cb the callback we want to suspend.