From: Paul E. McKenney Date: Thu, 11 Dec 2014 18:20:59 +0000 (-0800) Subject: rcu: Improve diagnostics for spurious RCU CPU stall warnings X-Git-Tag: fixes-v4.0-rc1~182^2^2^5~6 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=6ccd2ecd422644277b7d8b37222e3af3f43ea9ae;p=pandora-kernel.git rcu: Improve diagnostics for spurious RCU CPU stall warnings The current RCU CPU stall warning code will print "Stall ended before state dump start" any time that the stall-warning code is triggered on a CPU that has already reported a quiescent state for the current grace period and if all quiescent states have been reported for the current grace period. However, a true stall can result in these symptoms, for example, by preventing RCU's grace-period kthreads from ever running This commit therefore checks for this condition, reporting the end of the stall only if one of the grace-period counters has actually advanced. Otherwise, it reports the last time that the grace-period kthread made meaningful progress. (In normal situations, the grace-period kthread should make meaningful progress at least every jiffies_till_next_fqs jiffies.) Reported-by: Miroslav Benes Signed-off-by: Paul E. McKenney Tested-by: Miroslav Benes --- Reading git-diff-tree failed