On 03/16, Konstantin Khlebnikov wrote: > > On 16.03.2015 17:07, Oleg Nesterov wrote: >> I mean, I think we can do another cleanup on top of this change. >> >> 1. set_mm_exe_file() should be called by exit/exec only, so >> it should use >> >> rcu_dereference_protected(mm->exe_file, >> atomic_read(&mm->mm_users) <= 1); >> >> 2. prctl() should not use it, it can do >> >> get_file(new_exe); >> old_exe = xchg(&mm->exe_file); >> if (old_exe) >> fput(old_exe); > > I think smp_mb() is required before xchg() or > probably this stuff should be hidden inside yet another magic RCU macro > ( with two screens of comments =) Not really, xchg() implies mb's on both sides. As any other atomic operation which returns the result. (And in fact we do not even need rcu_assign_pointer() in set_mm_exe_file(), get_mm_exe_file() could do READ_ONCE() + inc_not_zero(). But this is off- topic, and of course rcu_* helpers look better) Oleg. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>