New submission from Brett Tiplitz: When running the example mmap library (with a slight modification, plus I did not handle all the changes for the 3.3 string handling as the example posted does not work with 3.x)
When looking at the subprocess, the spawned process will have all the mmap'd file descriptors open. The spawned process has the responsibility of closing any FD's that are in use. However, since the shared memory segment get's closed and the program has no knowledge of private FD's, the mmap's private FD becomes a leak in the FD table. It seems python should set the close-on-exec attribute on the dup'd FD that it maintains. Examples of fixing this issue are found on http://stackoverflow.com/questions/1643304/how-to-set-close-on-exec-by-default import mmap,os # write a simple example file with open("hello.txt", "wb") as f: f.write(bytes("Hello Python!\n", 'UTF-8')) with open("hello.txt", "r+b") as f: # memory-map the file, size 0 means whole file os.system("/bin/ls -l /proc/"+str(os.getpid())+"/fd") mm = mmap.mmap(f.fileno(), 0) os.system("/bin/ls -l /proc/"+str(os.getpid())+"/fd") os.system("/bin/ls -l /proc/self/fd") # read content via standard file methods t1 = mm.readline() # used to print out # prints "Hello Python!" # read content via slice notation t2=mm[:5] # print mm[:5] # prints "Hello" # update content using slice notation; # note that new content must have same size mm[6:] = bytes(" world!\n", 'UTF-8') # ... and read again using standard file methods mm.seek(0) t3=mm.readline() # print mm.readline() # prints "Hello world!" # close the map mm.close() ~ ---------- components: Library (Lib) messages: 206871 nosy: btiplitz priority: normal severity: normal status: open title: wrong behavior with fork and mmap type: behavior versions: Python 2.7 _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue20057> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
