On Fri, 02 Oct 2015 18:11:53 +0200, Gilles Chanteperdrix said: > TRACE_IRQFLAGS is broken with the I-pipe patch. At least on ARM. The > visible result is LOCKDEP false positives, but there may be some > more subtle kernel data structures corruption due to the fact that > the TRACE_IRQFLAFGS code is called from the Xenomai context. The > principle of Xenomai is to be able to run while Linux believes > its interrupts are off, in the middle of its critical sections. For > this to be possible, the code run in this context must never touch > any Linux kernel data structures. Enabling TRACE_IRQFLAGS breaks > this assumption: Linux code which potentially accesses Linux data > structures gets called from the Xenomai context. The consequences > can be anything, such as mlock failing, though in practice we never > get any report about that. The usual reason for mlockall failing is > because the user is not root, and with default ulimit settings at > least, mlockall can not be called by non-root users. Thanks for the detailed explanation - It's a refreshing change from the usual cargo-cult programming "It seems to break but we have no idea why, so just turn it off" we often see with out-of-tree patches. One thing jumped out at me: > The principle of Xenomai is to be able to run while Linux believes > its interrupts are off, in the middle of its critical sections Are you saying that it enables interrupts when Linux thinks they are off? If so, all I can say is: You're a far braver man than I. :)
Attachment:
pgpcx3NXJUzCo.pgp
Description: PGP signature
_______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
