Message ID | 20200524215739.551568-6-bigeasy@linutronix.de |
---|---|
State | Not Applicable |
Delegated to: | David Miller |
Headers | show |
Series | None | expand |
* Sebastian Andrzej Siewior <bigeasy@linutronix.de> wrote: > From: Mike Galbraith <umgwanakikbuti@gmail.com> > > send_msg() disables preemption to avoid out-of-order messages. As the > code inside the preempt disabled section acquires regular spinlocks, > which are converted to 'sleeping' spinlocks on a PREEMPT_RT kernel and > eventually calls into a memory allocator, this conflicts with the RT > semantics. > > Convert it to a local_lock which allows RT kernels to substitute them with > a real per CPU lock. On non RT kernels this maps to preempt_disable() as > before. No functional change. > > [bigeasy: Patch description] > > Cc: Evgeniy Polyakov <zbr@ioremap.net> > Cc: netdev@vger.kernel.org > Signed-off-by: Mike Galbraith <umgwanakikbuti@gmail.com> > Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> > --- > drivers/connector/cn_proc.c | 22 +++++++++++++++------- > 1 file changed, 15 insertions(+), 7 deletions(-) > > diff --git a/drivers/connector/cn_proc.c b/drivers/connector/cn_proc.c > index d58ce664da843..d424d1f469136 100644 > --- a/drivers/connector/cn_proc.c > +++ b/drivers/connector/cn_proc.c > @@ -18,6 +18,7 @@ > #include <linux/pid_namespace.h> > > #include <linux/cn_proc.h> > +#include <linux/locallock.h> > > /* > * Size of a cn_msg followed by a proc_event structure. Since the > @@ -38,25 +39,32 @@ static inline struct cn_msg *buffer_to_cn_msg(__u8 *buffer) > static atomic_t proc_event_num_listeners = ATOMIC_INIT(0); > static struct cb_id cn_proc_event_id = { CN_IDX_PROC, CN_VAL_PROC }; > > -/* proc_event_counts is used as the sequence number of the netlink message */ > -static DEFINE_PER_CPU(__u32, proc_event_counts) = { 0 }; > +/* local_evt.counts is used as the sequence number of the netlink message */ > +struct local_evt { > + __u32 counts; > + struct local_lock lock; > +}; > +static DEFINE_PER_CPU(struct local_evt, local_evt) = { > + .counts = 0, I don't think zero initializations need to be written out explicitly. > + .lock = INIT_LOCAL_LOCK(lock), > +}; > > static inline void send_msg(struct cn_msg *msg) > { > - preempt_disable(); > + local_lock(&local_evt.lock); > > - msg->seq = __this_cpu_inc_return(proc_event_counts) - 1; > + msg->seq = __this_cpu_inc_return(local_evt.counts) - 1; Naming nit: renaming this from 'proc_event_counts' to 'local_evt.counts' is a step back IMO - what's an 'evt', did we run out of e's? ;-) Should be something like local_event.count? (Singular.) Thanks, Ingo
On 2020-05-25 09:18:19 [+0200], Ingo Molnar wrote: > > +static DEFINE_PER_CPU(struct local_evt, local_evt) = { > > + .counts = 0, > > I don't think zero initializations need to be written out explicitly. yes. > > + .lock = INIT_LOCAL_LOCK(lock), > > +}; > > > > static inline void send_msg(struct cn_msg *msg) > > { > > - preempt_disable(); > > + local_lock(&local_evt.lock); > > > > - msg->seq = __this_cpu_inc_return(proc_event_counts) - 1; > > + msg->seq = __this_cpu_inc_return(local_evt.counts) - 1; > > Naming nit: renaming this from 'proc_event_counts' to > 'local_evt.counts' is a step back IMO - what's an 'evt', > did we run out of e's? ;-) > > Should be something like local_event.count? (Singular.) okay. > Thanks, > > Ingo Sebastian
diff --git a/drivers/connector/cn_proc.c b/drivers/connector/cn_proc.c index d58ce664da843..d424d1f469136 100644 --- a/drivers/connector/cn_proc.c +++ b/drivers/connector/cn_proc.c @@ -18,6 +18,7 @@ #include <linux/pid_namespace.h> #include <linux/cn_proc.h> +#include <linux/locallock.h> /* * Size of a cn_msg followed by a proc_event structure. Since the @@ -38,25 +39,32 @@ static inline struct cn_msg *buffer_to_cn_msg(__u8 *buffer) static atomic_t proc_event_num_listeners = ATOMIC_INIT(0); static struct cb_id cn_proc_event_id = { CN_IDX_PROC, CN_VAL_PROC }; -/* proc_event_counts is used as the sequence number of the netlink message */ -static DEFINE_PER_CPU(__u32, proc_event_counts) = { 0 }; +/* local_evt.counts is used as the sequence number of the netlink message */ +struct local_evt { + __u32 counts; + struct local_lock lock; +}; +static DEFINE_PER_CPU(struct local_evt, local_evt) = { + .counts = 0, + .lock = INIT_LOCAL_LOCK(lock), +}; static inline void send_msg(struct cn_msg *msg) { - preempt_disable(); + local_lock(&local_evt.lock); - msg->seq = __this_cpu_inc_return(proc_event_counts) - 1; + msg->seq = __this_cpu_inc_return(local_evt.counts) - 1; ((struct proc_event *)msg->data)->cpu = smp_processor_id(); /* - * Preemption remains disabled during send to ensure the messages are - * ordered according to their sequence numbers. + * local_lock() disables preemption during send to ensure the messages + * are ordered according to their sequence numbers. * * If cn_netlink_send() fails, the data is not sent. */ cn_netlink_send(msg, 0, CN_IDX_PROC, GFP_NOWAIT); - preempt_enable(); + local_unlock(&local_evt.lock); } void proc_fork_connector(struct task_struct *task)