On Thu, 15 Oct 2009, John Kacur wrote: > > > From: Joerg Abraham <Joerg.Abraham@xxxxxxxxxxxxxxxxx> > > Date: Thu, Oct 15, 2009 at 7:51 PM > > Subject: 2.6.31.4-rt14 posix message queues problem > > To: LKML <linux-kernel@xxxxxxxxxxxxxxx> > > > > > > Hi, > > > > During some performance measurement I stumbled over unexpected bad > > results for a posix message queue test case. Which is not surprising > > since the kernel log shows a "BUG: scheduling while atomic:" on every > > measurement trigger. > > > > Attached is the kernel log for an embedded 8572ds powerpc system and a > > condensed user space test appli. The test appli uses 2 processes > > (mq_server and mq_client) and pingpongs some messages via posix > > message queues. Please see the c-file header for details (the appli > > itself makes not much sense but shows the problem). > > > > ./mq_server > > ./mq_client # just crashes during run > > > > The problem does _not_ occur on kernels 2.6.29.6-rt24, 2.6.29.6 > > vanilla and 2.6.31.4 vanilla. The problem does _also_ show up on an > > embedded x86_64 system and a full featured fc11 x86_64 system running > > a 2.6.31.4-rt14 based kernel, so I dont think it's arch dependent. > > > > Can anybody reproduce the crash ??? > > > > If you need more info's please let me know. > > > > [And if I'm doing stupid things just forgive me] > > > > Thanx > > > > Joerg > > Hello Joerg > > Does the following patch solve your problem? > > From 69fde4357db4a054733cbca4158606160e821a3a Mon Sep 17 00:00:00 2001 > From: John Kacur <jkacur@xxxxxxxxxx> > Date: Thu, 15 Oct 2009 20:52:37 +0200 > Subject: [PATCH] preempt_disable_rt(); should be paired with preempt_enable_rt() > > Signed-off-by: John Kacur <jkacur@xxxxxxxxxx> > --- > ipc/mqueue.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/ipc/mqueue.c b/ipc/mqueue.c > index 63a47f7..ab4df36 100644 > --- a/ipc/mqueue.c > +++ b/ipc/mqueue.c > @@ -830,7 +830,7 @@ static inline void pipelined_send(struct mqueue_inode_info *info, > wake_up_process(receiver->task); > smp_wmb(); > receiver->state = STATE_READY; > - preempt_enable_nort(); > + preempt_enable_rt(); > } > > /* pipelined_receive() - if there is task waiting in sys_mq_timedsend() > -- > 1.6.0.6 > > fyi: I completed my testing, and I was able to reproduce your problem on v2.6.31.4-rt14, and it goes away with the above patch. Cheers John -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
