| Message ID | 1432204221-1933-1-git-send-email-alban@endocode.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, 21 May 2015 12:30:21 +0200 Alban Crequy <alban.crequy@gmail.com> wrote: > commit 818411616baf ("fs, proc: introduce > /proc/<pid>/task/<tid>/children entry") introduced the children entry > for checkpoint restore and the file is only available on kernels > configured with CONFIG_EXPERT and CONFIG_CHECKPOINT_RESTORE. > > This is available in most distributions (Fedora, Debian, Ubuntu, CoreOS) > because they usually enable CONFIG_EXPERT and CONFIG_CHECKPOINT_RESTORE. > But Arch does not enable CONFIG_EXPERT or CONFIG_CHECKPOINT_RESTORE. > > However, the children proc file is useful outside of checkpoint restore. > I would like to use it in rkt. The rkt process exec() another program it > does not control, and that other program will fork()+exec() a child > process. I would like to find the pid of the child process from an > external tool without iterating in /proc over all processes to find > which one has a parent pid equal to rkt. > > Since the children proc file is useful outside of checkpoint-restore, > I am removing the guard on CONFIG_CHECKPOINT_RESTORE. This will add a lump of code to kernels which don't need it. It's a bit of a pain, but I suppose we should still keep the presence of get_children_pid() configurable. That would be by adding a new CONFIG_PROC_CHILDREN (or similar) and making CONFIG_CHECKPOINT_RESTORE select that. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, May 21, 2015 at 3:30 AM, Alban Crequy <alban.crequy@gmail.com> wrote: > From: Alban Crequy <alban@endocode.com> > > commit 818411616baf ("fs, proc: introduce > /proc/<pid>/task/<tid>/children entry") introduced the children entry > for checkpoint restore and the file is only available on kernels > configured with CONFIG_EXPERT and CONFIG_CHECKPOINT_RESTORE. > > This is available in most distributions (Fedora, Debian, Ubuntu, CoreOS) > because they usually enable CONFIG_EXPERT and CONFIG_CHECKPOINT_RESTORE. > But Arch does not enable CONFIG_EXPERT or CONFIG_CHECKPOINT_RESTORE. > > However, the children proc file is useful outside of checkpoint restore. > I would like to use it in rkt. The rkt process exec() another program it > does not control, and that other program will fork()+exec() a child > process. I would like to find the pid of the child process from an > external tool without iterating in /proc over all processes to find > which one has a parent pid equal to rkt. > > Since the children proc file is useful outside of checkpoint-restore, > I am removing the guard on CONFIG_CHECKPOINT_RESTORE. I sent an essentially identical patch a couple years ago, and it got some interesting comments: http://lkml.kernel.org/g/0e00e9073855c02a382d49ba1ede9c4fda3451b7.1372189875.git.luto@amacapital.net See also: http://lkml.kernel.org/g/5f9a6b3ab75b12f2c5ba61ea1f6f3b08e9952b55.1372280661.git.luto@amacapital.net --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, May 21, 2015 at 02:47:33PM -0700, Andy Lutomirski wrote: > > > > Since the children proc file is useful outside of checkpoint-restore, > > I am removing the guard on CONFIG_CHECKPOINT_RESTORE. > > I sent an essentially identical patch a couple years ago, and it got > some interesting comments: > Oh, it is 2k13, I thought it's merged already ;) > http://lkml.kernel.org/g/0e00e9073855c02a382d49ba1ede9c4fda3451b7.1372189875.git.luto@amacapital.net > > See also: > > http://lkml.kernel.org/g/5f9a6b3ab75b12f2c5ba61ea1f6f3b08e9952b55.1372280661.git.luto@amacapital.net -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, May 21, 2015 at 11:47 PM, Andy Lutomirski <luto@amacapital.net> wrote: > On Thu, May 21, 2015 at 3:30 AM, Alban Crequy <alban.crequy@gmail.com> wrote: >> From: Alban Crequy <alban@endocode.com> >> >> commit 818411616baf ("fs, proc: introduce >> /proc/<pid>/task/<tid>/children entry") introduced the children entry >> for checkpoint restore and the file is only available on kernels >> configured with CONFIG_EXPERT and CONFIG_CHECKPOINT_RESTORE. >> >> This is available in most distributions (Fedora, Debian, Ubuntu, CoreOS) >> because they usually enable CONFIG_EXPERT and CONFIG_CHECKPOINT_RESTORE. >> But Arch does not enable CONFIG_EXPERT or CONFIG_CHECKPOINT_RESTORE. >> >> However, the children proc file is useful outside of checkpoint restore. >> I would like to use it in rkt. The rkt process exec() another program it >> does not control, and that other program will fork()+exec() a child >> process. I would like to find the pid of the child process from an >> external tool without iterating in /proc over all processes to find >> which one has a parent pid equal to rkt. >> >> Since the children proc file is useful outside of checkpoint-restore, >> I am removing the guard on CONFIG_CHECKPOINT_RESTORE. > > I sent an essentially identical patch a couple years ago, and it got > some interesting comments: > > http://lkml.kernel.org/g/0e00e9073855c02a382d49ba1ede9c4fda3451b7.1372189875.git.luto@amacapital.net Thanks for the pointer, I didn't see it. > See also: > > http://lkml.kernel.org/g/5f9a6b3ab75b12f2c5ba61ea1f6f3b08e9952b55.1372280661.git.luto@amacapital.net Your paragraph seems good to have in the documentation but I am also not qualified to comment on the behavior. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/fs/proc/array.c b/fs/proc/array.c index fd02a9e..6edec57 100644 --- a/fs/proc/array.c +++ b/fs/proc/array.c @@ -569,7 +569,6 @@ int proc_pid_statm(struct seq_file *m, struct pid_namespace *ns, return 0; } -#ifdef CONFIG_CHECKPOINT_RESTORE static struct pid * get_children_pid(struct inode *inode, struct pid *pid_prev, loff_t pos) { @@ -692,4 +691,3 @@ const struct file_operations proc_tid_children_operations = { .llseek = seq_lseek, .release = children_seq_release, }; -#endif /* CONFIG_CHECKPOINT_RESTORE */ diff --git a/fs/proc/base.c b/fs/proc/base.c index 093ca14..b743007 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -2922,9 +2922,7 @@ static const struct pid_entry tid_base_stuff[] = { ONE("stat", S_IRUGO, proc_tid_stat), ONE("statm", S_IRUGO, proc_pid_statm), REG("maps", S_IRUGO, proc_tid_maps_operations), -#ifdef CONFIG_CHECKPOINT_RESTORE REG("children", S_IRUGO, proc_tid_children_operations), -#endif #ifdef CONFIG_NUMA REG("numa_maps", S_IRUGO, proc_tid_numa_maps_operations), #endif