diff options
| author | Mike Galbraith <umgwanakikbuti@gmail.com> | 2020-05-27 22:11:17 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2020-05-28 10:31:10 +0200 |
| commit | 3e92fd7bd2b8418b53cb7304855b8b69bedbe2b4 (patch) | |
| tree | 927d18b1edc42b24367726fbdeea650e5b182149 | |
| parent | fd56200a16c72c7c3ec3e54e06160dfaa5b8dee8 (diff) | |
connector/cn_proc: Protect send_msg() with a local lock
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]
Signed-off-by: Mike Galbraith <umgwanakikbuti@gmail.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20200527201119.1692513-6-bigeasy@linutronix.de
| -rw-r--r-- | drivers/connector/cn_proc.c | 21 |
1 files changed, 14 insertions, 7 deletions
diff --git a/drivers/connector/cn_proc.c b/drivers/connector/cn_proc.c index d58ce664da84..646ad385e490 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/local_lock.h> /* * Size of a cn_msg followed by a proc_event structure. Since the @@ -38,25 +39,31 @@ 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_event.count is used as the sequence number of the netlink message */ +struct local_event { + local_lock_t lock; + __u32 count; +}; +static DEFINE_PER_CPU(struct local_event, local_event) = { + .lock = INIT_LOCAL_LOCK(lock), +}; static inline void send_msg(struct cn_msg *msg) { - preempt_disable(); + local_lock(&local_event.lock); - msg->seq = __this_cpu_inc_return(proc_event_counts) - 1; + msg->seq = __this_cpu_inc_return(local_event.count) - 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_event.lock); } void proc_fork_connector(struct task_struct *task) |