Messages in this thread |  | | Date | Tue, 24 Mar 2015 20:13:31 +0300 | | From | Konstantin Khlebnikov <> | | Subject | Re: [PATCH] mm: fix lockdep build in rcu-protected get_mm_exe_file() |
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On 23.03.2015 22:10, Oleg Nesterov wrote: > On 03/23, Davidlohr Bueso wrote: >> >> void set_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file) >> { >> struct file *old_exe_file = rcu_dereference_protected(mm->exe_file, >> - !atomic_read(&mm->mm_users) || current->in_execve || >> - lock_is_held(&mm->mmap_sem)); >> + !atomic_read(&mm->mm_users) || current->in_execve); > > Thanks, looks correct at first glance... > > But can't we remove the ->in_execve check above? and check > > atomic_read(&mm->mm_users) <= 1 > > instead. OK, this is subjective, I won't insist. Just current->in_execve > looks a bit confusing, it means "I swear, the caller is flush_old_exec() > and this mm is actualy bprm->mm". > > "atomic_read(&mm->mm_users) <= 1" looks a bit more "safe". But again, > I won't insist.
Not so safe: this will race with get_task_mm(). A lot of proc files grab temporary reference to task mm. But this just a debug -- we can place here "true".
> > Oleg. >
-- Konstantin
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