IFIX: Fixing Concurrency Bugs While They Are Introduced

Concurrency bugs are notoriously hard to identify and fix. A systematic way of avoiding concurrency bugs is to design and implement a locking policy that consistently guards all shared variables. Concurrency bugs thus can be viewed as the result of an illy-designed or poorly implemented locking policy. The trouble is that the locking policy is often not documented, which makes debugging concurrency bugs clueless. We argue that it is too late to debug concurrency bugs after programming is done and we instead detect and fix them while they are being implemented. In this work, we propose an approach named IFIX which flags potential concurrency bugs and recommends fixes while the bugs are introduced. The key idea is to automatically conjecture what the intended locking policy is based on static analysis and recommend fixes accordingly. The recommended fixes are present to the programmer promptly and the user feedback (i.e., whether the certain recommendation is selected) is used to refine the conjectured locking policy and consequently future fixes. IFIX is evaluated on 43 concurrent programs, and through a user study with 30 programmers. The experiment results and user feedback show that IFIX is efficient, accurate and user-friendly.