DragonFlyBSD

Hello,

I've observed both behaviors too.

The hang is a deadlock between the father process (truss) and the child
being exec'ed (e.g. ls). The father waits for the child to stop in
procfs_ioctl (PIOCWAIT). The child waits in PSTALL in
exec_new_vmspace() for the father to PRELE its reference to the
child.

This deadlocks because of pfs_find() which PHOLD's the child at the
beginning of procfs_ioctl() and keeps the reference while sleeping.

One possible fix would be to keep track of the number of
procfs_ioctl(PIOCWAIT) sleepers and adjust the expected lock count
passed to PSTALL (there is already such an adjustment for the vfork()
case). This requires adding a new field to struct proc though. I'm
in the process of trying this.

As an aside the tests for P_INEXEC in procfs_open() and procfs_ioctl()
are suspicious. The flag could be set just after being tested.

Cheers,
Nicolas

On 25 February 2012 17:24, Venkatesh Srinivas via Redmine
<bugtracker-admin@leaf.dragonflybsd.org> wrote:

Issue #2313 has been reported by Venkatesh Srinivas.

----------------------------------------
Bug #2313: truss doesn't work on 3.0/ -master
http://bugs.dragonflybsd.org/issues/2313

Author: Venkatesh Srinivas
Status: New
Priority: Normal
Assignee:
Category:
Target version:

truss on master stalls on 'exec1' or enters a loop of::

truss: PIOCWAIT top of loop: Inappropriate ioctl for device
truss: PIOCCONT: Inappropriate ioctl for device

when tracing /bin/ls, among other programs.

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Nicolas -- were you working on this? Or just commenting where the problems were?

Thanks!

Nicolas -- Happen to have an update wrt truss? How's it going?