On Wed, Aug 14, 2019 at 09:50:03AM +0000, Pavel Emelianov wrote: > On 8/12/19 11:09 PM, Adrian Reber wrote: > > The main motivation to add set_tid to clone3() is CRIU. > > > > To restore a process with the same PID/TID CRIU currently uses > > /proc/sys/kernel/ns_last_pid. It writes the desired (PID - 1) to > > ns_last_pid and then (quickly) does a clone(). This works most of the > > time, but it is racy. It is also slow as it requires multiple syscalls. > > > > Extending clone3() to support set_tid makes it possible restore a > > process using CRIU without accessing /proc/sys/kernel/ns_last_pid and > > race free (as long as the desired PID/TID is available). > > > > This clone3() extension places the same restrictions (CAP_SYS_ADMIN) > > on clone3() with set_tid as they are currently in place for ns_last_pid. > > > > Signed-off-by: Adrian Reber <[email protected]> > > Acked-by: Pavel Emelyanov <[email protected]>
On Tue, Aug 13, 2019 at 04:30:24PM +0200, Oleg Nesterov wrote: > On 08/12, Adrian Reber wrote: > > > > The main motivation to add set_tid to clone3() is CRIU. > > > > To restore a process with the same PID/TID CRIU currently uses > > /proc/sys/kernel/ns_last_pid. It writes the desired (PID - 1) to > > ns_last_pid and then (quickly) does a clone(). This works most of the > > time, but it is racy. It is also slow as it requires multiple syscalls. > > > > Extending clone3() to support set_tid makes it possible restore a > > process using CRIU without accessing /proc/sys/kernel/ns_last_pid and > > race free (as long as the desired PID/TID is available). > > > > This clone3() extension places the same restrictions (CAP_SYS_ADMIN) > > on clone3() with set_tid as they are currently in place for ns_last_pid. > > > > Signed-off-by: Adrian Reber <[email protected]> > > Reviewed-by: Oleg Nesterov <[email protected]> > Added-to: https://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux.git/log/?h=pidfd Merged-into: https://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux.git/log/?h=for-next Thanks! Christian
