tracing: Fix hwlat kthread migration

The hwlat tracer creates a kernel thread at start of the tracer. It is
pinned to a single CPU and will move to the next CPU after each period of
running. If the user modifies the migration thread's affinity, it will not
change after that happens.

The original code created the thread at the first instance it was called,
but later was changed to destroy the thread after the tracer was finished,
and would not be created until the next instance of the tracer was
established. The code that initialized the affinity was only called on the
initial instantiation of the tracer. After that, it was not initialized, and
the previous affinity did not match the current newly created one, making
it appear that the user modified the thread's affinity when it did not, and
the thread failed to migrate again.

Cc: stable@vger.kernel.org
Fixes: 0330f7aa8ee6 ("tracing: Have hwlat trace migrate across tracing_cpumask CPUs")
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

path: root/net/rds/info.h

#ifndef _RDS_INFO_H
#define _RDS_INFO_H

struct rds_info_lengths {
	unsigned int	nr;
	unsigned int	each;
};

struct rds_info_iterator;

/*
 * These functions must fill in the fields of @lens to reflect the size
 * of the available info source.  If the snapshot fits in @len then it
 * should be copied using @iter.  The caller will deduce if it was copied
 * or not by comparing the lengths.
 */
typedef void (*rds_info_func)(struct socket *sock, unsigned int len,
			      struct rds_info_iterator *iter,
			      struct rds_info_lengths *lens);

void rds_info_register_func(int optname, rds_info_func func);
void rds_info_deregister_func(int optname, rds_info_func func);
int rds_info_getsockopt(struct socket *sock, int optname, char __user *optval,
			int __user *optlen);
void rds_info_copy(struct rds_info_iterator *iter, void *data,
		   unsigned long bytes);
void rds_info_iter_unmap(struct rds_info_iterator *iter);


#endif