From: Ben Segall Date: Mon, 19 May 2014 22:49:45 +0000 (-0700) Subject: sched/fair: Fix unlocked reads of some cfs_b->quota/period X-Git-Tag: omap-for-v3.16/fixes-against-rc1~33^2~18 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=51f2176d74ace4c3f58579a605ef5a9720befb00;p=pandora-kernel.git sched/fair: Fix unlocked reads of some cfs_b->quota/period sched_cfs_period_timer() reads cfs_b->period without locks before calling do_sched_cfs_period_timer(), and similarly unthrottle_offline_cfs_rqs() would read cfs_b->period without the right lock. Thus a simultaneous change of bandwidth could cause corruption on any platform where ktime_t or u64 writes/reads are not atomic. Extend cfs_b->lock from do_sched_cfs_period_timer() to include the read of cfs_b->period to solve that issue; unthrottle_offline_cfs_rqs() can just use 1 rather than the exact quota, much like distribute_cfs_runtime() does. There is also an unlocked read of cfs_b->runtime_expires, but a race there would only delay runtime expiry by a tick. Still, the comparison should just be != anyway, which clarifies even that problem. Signed-off-by: Ben Segall Tested-by: Roman Gushchin [peterz: Fix compile warn] Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/r/20140519224945.20303.93530.stgit@sword-of-the-dawn.mtv.corp.google.com Cc: pjt@google.com Cc: Linus Torvalds Signed-off-by: Ingo Molnar --- Reading git-diff-tree failed