Reproduced on RHEL-7 with
strace-4.8-3.el7
kernel-3.10.0-23.el7
+++ This bug was initially created as a clone of Bug #1035433 +++
Description of problem:
When using strace to debug an LXC problem I noticed that it gets a bit confused by PID namespaces.
I am running strace from host context, so I expect all PIDs it reports to be host PIDs. When strace creates new log files (due to the -ff CLI option) it names them based on the host PIDs, which is good. Inside these log files though the clone() syscalls are reporting container PIDs which is bad. This means you can't correlate the clone() syscalls with the log files strace is creating.
If running strace from inside container context it correctly uses container PIDs in both places.
Version-Release number of selected component (if applicable):
strace-4.8-1.fc19.x86_64
kernel-3.11.9-200.fc19.x86_64
How reproducible:
Always
Steps to Reproduce:
1. From the host run
# strace -f -ff -o s.log unshare --pid -- /bin/sh
and at the shell prompt execute '/bin/sh' again. Then do it again. And again.. Then exit back to the host context
You should now have several log files
Actual results:
# ls s.log.*
s.log.9851 s.log.9860 s.log.9861 s.log.9862
# grep clone s.log.98*
s.log.9851:clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x7fe81e7b6a10) = 9860
s.log.9860:clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x7f47d93aca10) = 2
s.log.9861:clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x7f9962d34a10) = 3
Expected results:
# ls s.log.*
s.log.9851 s.log.9860 s.log.9861 s.log.9862
# grep clone s.log.98*
s.log.9851:clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x7fe81e7b6a10) = 9860
s.log.9860:clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x7f47d93aca10) = 9861
s.log.9861:clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x7f9962d34a10) = 9862
Additional info: