[PATCH v2 5/7] connector/cn_proc: Protect send_msg() with a local lock
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: 2020-05-24 21:58:23
Also in:
lkml
Subsystem:
networking drivers, the rest · Maintainers:
Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
From: Mike Galbraith <redacted> 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 <redacted> Cc: netdev@vger.kernel.org Signed-off-by: Mike Galbraith <redacted> 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, + .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)
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2.27.0.rc0