On Tue, Nov 24, 2015 at 11:52:12PM +0800, Boqun Feng wrote: > Hi Daniel, > > On Tue, Nov 24, 2015 at 02:03:06PM +0100, Daniel Wagner wrote: > > rcu_nocb_gp_cleanup() is called while holding rnp->lock. Currently, > > this is okay because the wake_up_all() in rcu_nocb_gp_cleanup() will > > not enable the IRQs. lockdep is happy. > > > > By switching over using swait this is not true anymore. swake_up_all() > > enables the IRQs while processing the waiters. __do_softirq() can now > > run and will eventually call rcu_process_callbacks() which wants to > > grap nrp->lock. > > > > Let's move the rcu_nocb_gp_cleanup() call outside the lock before we > > switch over to swait. > > > > But you did introduce swait in this patch ;-) > > [snip] > > > > > Signed-off-by: Daniel Wagner <daniel.wagner@xxxxxxxxxxxx> > > Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx> > > Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> > > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > > Cc: linux-kernel@xxxxxxxxxxxxxxx > > --- > > kernel/rcu/tree.c | 4 +++- > > kernel/rcu/tree.h | 3 ++- > > kernel/rcu/tree_plugin.h | 16 +++++++++++++--- > > 3 files changed, 18 insertions(+), 5 deletions(-) > > > > So I tried to build this patch with a config having RCU_EXPERT=y and > RCU_NOCB_CPU=y, but I got: > > In file included from include/linux/completion.h:11:0, > from include/linux/rcupdate.h:43, > from include/linux/sysctl.h:25, > from include/linux/timer.h:242, > from include/linux/workqueue.h:8, > from include/linux/pm.h:25, > from ./arch/x86/include/asm/apic.h:5, > from ./arch/x86/include/asm/smp.h:12, > from include/linux/smp.h:59, > from kernel/rcu/tree.c:34: > kernel/rcu/tree_plugin.h: In function ‘rcu_nocb_gp_cleanup’: > kernel/rcu/tree_plugin.h:1782:14: warning: passing argument 1 of ‘__wake_up’ from incompatible pointer type [-Wincompatible-pointer-types] > wake_up_all(sq); > ^ > include/linux/wait.h:168:36: note: in definition of macro ‘wake_up_all’ > #define wake_up_all(x) __wake_up(x, TASK_NORMAL, 0, NULL) > > Just to be clear, I saw this build error when I applied only the first four patches of this series. When I applied the whole series, I didn't see any build error. Regards, Boqun
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