On Wed, Sep 02, 2015 at 05:14:33PM -0700, Paul E. McKenney wrote: > On Wed, Sep 02, 2015 at 12:24:50PM -0400, Tejun Heo wrote: > > cc'ing Paul. > > > > On Wed, Sep 02, 2015 at 08:12:28AM -0500, Felipe Balbi wrote: > > > while booting AM437x device, the following splat > > > triggered: > > > > > > [ 12.005238] =============================== > > > [ 12.009749] [ INFO: suspicious RCU usage. ] > > > [ 12.014116] 4.2.0-next-20150831 #1154 Not tainted > > > [ 12.019050] ------------------------------- > > > [ 12.023408] security/device_cgroup.c:405 device_cgroup:verify_new_ex called without proper synchronization! > > ... > > > [ 12.128326] [<c0317a04>] (verify_new_ex) from [<c0317f50>] (devcgroup_access_write+0x374/0x658) > > > [ 12.137426] [<c0317f50>] (devcgroup_access_write) from [<c00d2800>] (cgroup_file_write+0x28/0x1bc) > > > [ 12.146796] [<c00d2800>] (cgroup_file_write) from [<c01f1670>] (kernfs_fop_write+0xc0/0x1b8) > > > [ 12.155620] [<c01f1670>] (kernfs_fop_write) from [<c0177c94>] (__vfs_write+0x1c/0xd8) > > > [ 12.163783] [<c0177c94>] (__vfs_write) from [<c0178594>] (vfs_write+0x90/0x16c) > > > [ 12.171426] [<c0178594>] (vfs_write) from [<c0178db4>] (SyS_write+0x44/0x9c) > > > [ 12.178806] [<c0178db4>] (SyS_write) from [<c000f680>] (ret_fast_syscall+0x0/0x1c) > > > > This shouldn't be happening because devcgroup_access_write() always > > grabs devcgroup_mutex. Looking at the log, the culprit seems to be > > f78f5b90c4ff ("rcu: Rename rcu_lockdep_assert() to > > RCU_LOCKDEP_WARN()"). It missed the bang for the second test while > > inverting it, so adding rcu_read_lock() isn't the right fix here. > > > > Paul, can you please fix it? > > Gah! Please see below. > > Thanx, Paul > > ------------------------------------------------------------------------ > > security/device_cgroup: Fix RCU_LOCKDEP_WARN() condition > > f78f5b90c4ff ("rcu: Rename rcu_lockdep_assert() to RCU_LOCKDEP_WARN()") > introduced a bug by incorrectly inverting the condition when moving from > rcu_lockdep_assert() to RCU_LOCKDEP_WARN(). This commit therefore fixes > the inversion. > > Reported-by: Felipe Balbi <balbi@xxxxxx> > Reported-by: Tejun Heo <tj@xxxxxxxxxx> > Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> > Cc: Serge Hallyn <serge@xxxxxxxxxx> Oh, makes sense :) (didn't see the original patch when it came by, sorry) Acked-by: Serge Hallyn <serge.hallyn@xxxxxxxxxxxxx> > diff --git a/security/device_cgroup.c b/security/device_cgroup.c > index 73455089feef..03c1652c9a1f 100644 > --- a/security/device_cgroup.c > +++ b/security/device_cgroup.c > @@ -401,7 +401,7 @@ static bool verify_new_ex(struct dev_cgroup *dev_cgroup, > bool match = false; > > RCU_LOCKDEP_WARN(!rcu_read_lock_held() && > - lockdep_is_held(&devcgroup_mutex), > + !lockdep_is_held(&devcgroup_mutex), > "device_cgroup:verify_new_ex called without proper synchronization"); > > if (dev_cgroup->behavior == DEVCG_DEFAULT_ALLOW) { -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html