|Summary:||sshd hangs on close|
|Product:||Process Management||Reporter:||Rafael J. Wysocki (rjw)|
|Component:||Preemption||Assignee:||Robert Love (rlove)|
|Bug Depends on:|
Description Rafael J. Wysocki 2008-08-30 13:26:40 UTC
Subject : sshd hangs on close Submitter : Matthias Urlichs <firstname.lastname@example.org> Date : 2008-08-30 9:18 References : http://marc.info/?l=linux-kernel&m=122008800512864&w=4 This entry is being used for tracking a regression from 2.6.26. Please don't close it until the problem is fixed in the mainline.
Comment 1 Matthias Urlichs 2008-09-14 13:09:52 UTC
Unfortunately, the problem seems to have permanently vanished after the affected machine has been rebooted with a known-good kernel, and has since resisted my attempts at reproducing it.
Comment 2 N K 2011-01-12 05:08:55 UTC
I am able to reproduce this problem on one machine with 2.6.32 (rhel6). It appears to be due to needing a kernel-thread 'events' to get cpu time on a foreign cpu. E.g. if sshd is running on cpu0, and cpu1 is shielded with a FIFO-99 process starving the kernel-thread 'events/1' (non-RT), sshd on cpu0 hangs with wchan=flush_cpu with the last strace being closing the filedescriptor of /dev/ptmx. Question1 - why does cpu0 wait for events/1? Question2 - why does sshd's close /dev/ptmx trigger this? Question3 - what exactly is wchan=cpu_flush indicating?