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When a thread executed an exit syscall in SE mode, the thread context was removed immediately in the same cycle, which left inflight squash operations and trap event incomplete. The problem happened when a new thread was assigned to the CPU later. The new thread started with some incomplete transactions of the previous thread (e.g., squashing). This problem could cause incorrect execution flow for the new thread (i.e., pc was not reset properly at the exit point), deadlock (i.e., some stage-to-stage signals were not reset) and incorrect rename map between logical and physical registers. This patch adds a new state called 'Halting' to the thread context and defers removing thread context from a CPU until a trap event initiated by an exit syscall execution is processed. This patch also makes sure that the removal of a thread context happens after all inflight transactions of the to-be-removed thread in the pipeline complete. Change-Id: If7ef1462fb8864e22b45371ee7ae67e2a5ad38b8 Reviewed-on: https://gem5-review.googlesource.com/c/8184 Reviewed-by: Giacomo Gabrielli <giacomo.gabrielli@arm.com> Maintainer: Jason Lowe-Power <jason@lowepower.com>
This is the gem5 simulator. The main website can be found at http://www.gem5.org A good starting point is http://www.gem5.org/Introduction, and for more information about building the simulator and getting started please see http://www.gem5.org/Documentation and http://www.gem5.org/Tutorials. To build gem5, you will need the following software: g++ or clang, Python (gem5 links in the Python interpreter), SCons, SWIG, zlib, m4, and lastly protobuf if you want trace capture and playback support. Please see http://www.gem5.org/Dependencies for more details concerning the minimum versions of the aforementioned tools. Once you have all dependencies resolved, type 'scons build/<ARCH>/gem5.opt' where ARCH is one of ALPHA, ARM, NULL, MIPS, POWER, SPARC, or X86. This will build an optimized version of the gem5 binary (gem5.opt) for the the specified architecture. See http://www.gem5.org/Build_System for more details and options. With the simulator built, have a look at http://www.gem5.org/Running_gem5 for more information on how to use gem5. The basic source release includes these subdirectories: - configs: example simulation configuration scripts - ext: less-common external packages needed to build gem5 - src: source code of the gem5 simulator - system: source for some optional system software for simulated systems - tests: regression tests - util: useful utility programs and files To run full-system simulations, you will need compiled system firmware (console and PALcode for Alpha), kernel binaries and one or more disk images. Please see the gem5 download page for these items at http://www.gem5.org/Download If you have questions, please send mail to gem5-users@gem5.org Enjoy using gem5 and please share your modifications and extensions.