On Thu, 2009-11-26 at 10:10 -0500, Oren Laadan wrote: > > Nathan Lynch wrote: > > The feeder thread can cause the restart process to fail by indirectly > > calling exit_group, which sends SIGKILL to all other threads in the > > process. If the feeder thread "wins" the race, the restart is > > disrupted. A common symptom of this race is the coordinator task > > returning from the wait_for_completion_interruptible in > > wait_all_tasks_finish with a signal (the SIGKILL) pending. > > So the clone mage page says: > ... > The main use of clone() is to implement threads: multiple threads > of control in a program that run concurrently in a shared memory > space. > ... > When the fn(arg) function application returns, the child process > terminates. The integer returned by fn is the exit code for the > child process. The child process may also terminate explicitly by > calling exit(2) or after receiving a fatal signal. > ... > (http://www.kernel.org/doc/man-pages/online/pages/man2/__clone2.2.html) > > I expected "terminates" here to mean invoke the syscall _exit(). > Clearly this is desirable with CLONE_THREAD, Calling _exit (as glibc's clone support code does) is clearly undesirable for CLONE_THREAD users such as restart.c because _exit calls exit_group, terminating the whole thread group. That's kind of the whole point of the patch :) > but not for regular > processes that will want to proceed to the usual glibc exit path > (e.g. process at_exit() and what-not). Then again, the last thread > to exit should also call glibc's exit for the same reason. So > that's probably why it's handled this way. > > This matters for us because our user-space wrapper to eclone() > should eventually do what the glibc's clone() wrapper does, instead > of calling _exit() directly as it is today... For compatibility's sake, the user-space eclone wrapper should eventually do what glibc's clone support code does, yes -- branch to _exit. But I think you've stated the case backwards? Currently the eclone wrappers call sys_exit directly (e.g. "li r0,__NR_exit; sc" on powerpc). _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers
