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authorMike Galbraith <umgwanakikbuti@gmail.com>2020-05-27 22:11:17 +0200
committerIngo Molnar <mingo@kernel.org>2020-05-28 10:31:10 +0200
commit3e92fd7bd2b8418b53cb7304855b8b69bedbe2b4 (patch)
tree927d18b1edc42b24367726fbdeea650e5b182149
parentfd56200a16c72c7c3ec3e54e06160dfaa5b8dee8 (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.c21
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)