Messages in this thread | | | Date | Sun, 1 Jul 2012 21:57:22 +0100 | From | Al Viro <> | Subject | Re: [PATCH 0/4] Was: deferring __fput() |
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On Sun, Jul 01, 2012 at 03:50:02PM -0400, Mimi Zohar wrote: > > I haven't mentioned the "ima: defer calling __fput()" patch, since I've > compiled git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs.git > #untested with a .config based on config-3.4.2-1.fc16.x86_64 and am > having this problem. No need to add more confusion. The "ima: defer > calling __fput()" will be dropped from the patchset, as soon as the > general method works. > > I've isolated the problem to the PF_KTHREAD section of fput(). > > void fput(struct file *file) > { > if (atomic_long_dec_and_test(&file->f_count)) { > struct task_struct *task = current; > file_sb_list_del(file); > if (unlikely(in_interrupt() || task->flags & PF_KTHREAD)) { > unsigned long flags; > spin_lock_irqsave(&delayed_fput_lock, flags); > list_add(&file->f_u.fu_list, &delayed_fput_list); > schedule_work(&delayed_fput_work); > spin_unlock_irqrestore(&delayed_fput_lock, flags); > return; > } > init_task_work(&file->f_u.fu_rcuhead, ____fput); > task_work_add(task, &file->f_u.fu_rcuhead, true); > } > } > > Replacing it with a call to __fput(), the system boots.
"it" being just the part under that if (unlikely(...)))? Very interesting... If so, we have some kernel thread ending up with delayed __fput() which somehow makes dracut (assuimg you are using fedora initramfs to go with fedora config) unhappy. With your own patch, doing async __fput() in a lot of cases when this one doesn't delay past the return to userland managing to survive the boot... I wonder which files end up triggering that fun and which kernel thread is responsible... Could you slap a printk() in there, showing file->f_dentry->d_inode->i_mode (octal) and at least file->f_dentry->d_name.name? Along with the current->comm[], all under that inner if (). And see which ones end up going that way by the time execve() of /sbin/init fails.
It would be nice to see which sys_mount() calls are made and which (if any) fail, BTW. I wonder if it even gets to mounting the right root...
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