| Message ID | 1320265849-5744-9-git-send-email-paulmck@linux.vnet.ibm.com |
|---|---|
| State | Accepted |
| Commit | 2c01531f08f8ba663a20d8472a3032f6df133b6e |
| Headers | show |
On Wed, Nov 02, 2011 at 01:30:30PM -0700, Paul E. McKenney wrote: > One of lclaudio's systems was seeing RCU CPU stall warnings from idle. > These turned out to be caused by a bug that stopped scheduling-clock > tick interrupts from being sent to a given CPU for several hundred seconds. Out of curiosity, what caused this bug? - Josh Triplett
On Wed, Nov 02, 2011 at 08:07:50PM -0700, Josh Triplett wrote: > On Wed, Nov 02, 2011 at 01:30:30PM -0700, Paul E. McKenney wrote: > > One of lclaudio's systems was seeing RCU CPU stall warnings from idle. > > These turned out to be caused by a bug that stopped scheduling-clock > > tick interrupts from being sent to a given CPU for several hundred seconds. > > Out of curiosity, what caused this bug? If I remember correctly, software/configuration bugs in the clock code. Thanx, Paul
diff --git a/Documentation/RCU/stallwarn.txt b/Documentation/RCU/stallwarn.txt index 4e95920..f3e0625 100644 --- a/Documentation/RCU/stallwarn.txt +++ b/Documentation/RCU/stallwarn.txt @@ -101,6 +101,11 @@ o A CPU-bound real-time task in a CONFIG_PREEMPT_RT kernel that CONFIG_TREE_PREEMPT_RCU case, you might see stall-warning messages. +o A hardware or software issue shuts off the scheduler-clock + interrupt on a CPU that is not in dyntick-idle mode. This + problem really has happened, and seems to be most likely to + result in RCU CPU stall warnings for CONFIG_NO_HZ=n kernels. + o A bug in the RCU implementation. o A hardware failure. This is quite unlikely, but has occurred
One of lclaudio's systems was seeing RCU CPU stall warnings from idle. These turned out to be caused by a bug that stopped scheduling-clock tick interrupts from being sent to a given CPU for several hundred seconds. This commit therefore updates the documentation to call this out as a possible cause for RCU CPU stall warnings. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> --- Documentation/RCU/stallwarn.txt | 5 +++++ 1 files changed, 5 insertions(+), 0 deletions(-)