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c31fc2f424
Fix an unusual C to Go callback case. Newly created C threads call into Go code, forcing the Go code to allocate new M and G structures. While executing Go code, the stack is split. The Go code then returns. Returning from a Go callback is treated as entering a system call, so the G gcstack field is set to point to the Go stack. In this case, though, we were called from a newly created C thread, so we drop the extra M and G structures. The C thread then exits. Then a new C thread calls into Go code, reusing the previously created M and G. The Go code requires a larger stack frame, causing the old stack segment to be unmapped and a new stack segment allocated. At this point the gcstack field is pointing to the old stack segment. Then a garbage collection occurs. The garbage collector sees that the gcstack field is not nil, so it scans it as the first stack segment. Unfortunately it points to memory that was unmapped. So the program crashes. The fix is simple: when handling extra G structures created for callbacks from new C threads, clear the gcstack field. From-SVN: r218699
See ../README. This is the runtime support library for the Go programming language. This library is intended for use with the Go frontend. The library has only been tested on GNU/Linux using glibc. It should not be difficult to port to other operating systems. The library has only been tested on x86/x86_64 systems. It should not be difficult to port to other architectures. Directories: go A copy of the Go library from http://golang.org/, with a few changes for gccgo. Notably, the reflection interface is different. runtime Runtime functions, written in C, which are called directly by the compiler or by the library. syscalls System call support. Contributing ============ To contribute patches to the files in this directory, please see http://golang.org/doc/gccgo_contribute.html . The master copy of these files is hosted at http://code.google.com/p/gofrontend . Changes to these files require signing a Google contributor license agreement. If you are the copyright holder, you will need to agree to the individual contributor license agreement at http://code.google.com/legal/individual-cla-v1.0.html. This agreement can be completed online. If your organization is the copyright holder, the organization will need to agree to the corporate contributor license agreement at http://code.google.com/legal/corporate-cla-v1.0.html. If the copyright holder for your code has already completed the agreement in connection with another Google open source project, it does not need to be completed again.