Using Formal Methods to Verify Transactional Abstract Concurrency Control

Concurrent application design and implementation is more important than ever in today\u27s multi-core processor world. Transactional Memory (TM) Concurrent application design and implementation is more important than ever in today\u27s multi-core processor world. Transactional Memory (TM). Each has its own particular advantages and disadvantages. However, these techniques each need some extra information to `glue\u27 the non-transactional operation into a transactional context. At the most general level, non-transactional code must be decorated in such a way that the TM run-time can determine how those non-transactional operations commute with one another, and how to `undo\u27 the non-transactional operations in case the run-time needs to abort a software transaction. The TM run-time trusts that these programmer-provided annotations are correct. Therefore, if an implementor needs to employ one of these transactional `escape hatches\u27, it is crucially important that their concurrency control annotations be correct. However, reasoning about the commutativity of data structure operations is often challenging, and increasing the burden on the programmer with a proof requirement does not simplify the task of concurrent programming. There is a way to leverage the structure that these TM extensions require to reduce greatly the burden on the programmer. If the programmer could describe the abstract state of the data structure and then reason about it with as much machine assistance as possible, then there would be much less opportunity for error. Abstract state is preferable to a more concrete state, because it permits the programmer to use different concrete implementations of the same abstract data type. Also, some TM extensions such as open nesting can handle concrete state conflicts without programmer intervention (making the abstract state the appropriate state for reasoning about commutativity). A solution to the problem of specifying and verifying the concurrency properties of abstract data structures is the subject of this thesis. We will describe a new language, ACCLAM, for describing the abstract state of a data structure and reasoning about its concurrency control properties. This thesis also describes a tool that can process ACCLAM descriptions into a machine verifiable form (they are converted to a SAT problem). We will also provides a more detailed overview of transactional memory and the more popular extensions, a detailed semantic description of ACCLAM and a set of example data structure models and the results of processing those examples with the language processing tool

Randomized Instruction Set Emulation To Disrupt Binary . . .

Many remote attacks against computer systems inject binary code into the execution path of a running program, gaining control of the program's behavior. If each defended system or program could use a machine instruction set that was both unique and private, such binary code injection attacks would become extremely difficult if not impossible. A binary-to-binary translator provides an economic and flexible implementation path for realizing that idea. As a proof of concept, we describe a randomized instruction set emulator (RISE) based on the open-source Valgrind x86-to-x86 binary translator. Although currently very slow and memory-intensive, our prototype RISE can indeed disrupt binary code injection attacks against a program without requiring its recompilation, linking, or access to source code. We describe the RISE implementation, give evidence demonstrating that RISE defeats common attacks, consider consequences of the dense x86 instruction set on the method's effects, and discuss limitations of the RISE prototype as well as design tradeoffs and extensions of the underlying idea

True bromance: the authenticity behind the Stewart/McKellen relationship

For public figures with high-profile roles, media interest in professional pursuits is a regular occurrence. When media attention turns from the public role to the private lives of public figures, suggests Graeme Turner, is the moment when a public figure becomes a celebrity. Specially, Richard Dyer suggests, interest in the private lives of celebrities is grounded in the notion that in the private resides the authentic person behind the ‘manufactured mask of fame’. The increasing popularity of social media, and celebrity figures’ use of such intimate platforms of performance, gives rise to a system of representation P. David Marshall terms ‘presentational culture’. A seemingly genuine persona is presented to the public, yet it is one that nonetheless attracts questions of authenticity, especially when that presentation coincides with promotional activities. This article examines the authenticity of the bromance between Ian McKellen and Patrick Stewart through the lens of their social media presence. The article explores the narrative of friendship constructed by the actors, and evaluates how their history as friends and recent promotional activity for the film X-Men Days of Future Past and the plays Waiting for Godot and No Man’s Land influence the perceived authenticity of their bromance

Comparison of BD Bactec Plus Aerobic/F Medium to VersaTREK Redox 1 Blood Culture Medium for Detection of Candida spp. in Seeded Blood Culture Specimens Containing Therapeutic Levels of Antifungal Agents▿

Recovery of Candida spp. using the BD Bactec FX blood culture (BC) system (Bactec Plus Aerobic/F medium) and the VersaTREK system (aerobic Redox medium) was evaluated using seeded BC bottles with and without the addition of commonly used antifungal agents. BC bottles (n = 1,442) were each inoculated with 10 ml human whole blood and 0.1 ml of suspensions of Candida spp., with or without antifungal agents. BC bottles were incubated in the corresponding system for a maximum of 5 days. In the absence of antifungal agents, Bactec FX recovered 97.4% of Candida spp., and VersaTREK recovered 99.1% (P = 0.154). With regard to length of time to detection (LTD) and overall recovery, both systems had various levels of effectiveness in recovering C. glabrata. In bottles containing antifungal agents, Bactec FX recovered 83.1% of isolates, whereas VersaTREK recovered 50.7% of Candida spp. (P < 0.001). For BC bottles without the addition of antifungal agents, the median LTD for VersaTREK was 2.2 h faster than that of Bactec FX (P < 0.001). In the presence of antifungal agents, the Bactec FX recovery time was significantly faster than that of VersaTREK (median difference of 10.8 h, P < 0.001). We conclude that both systems have comparable abilities to recover Candida spp. from seeded blood cultures in the absence of antifungal agents. In the presence of therapeutic levels of commonly used antifungal agents, the Bactec FX system demonstrated a significantly greater recovery of various Candida spp., as well as a shorter LTD