relay: Use per CPU constructs for the relay channel buffer pointers
relay essentially needs to maintain a per CPU array of channel buffer
pointers but it manually creates that array. Instead its better to use
the per CPU constructs, provided by the kernel, to allocate & access the
array of pointer to channel buffers.
Signed-off-by: Akash Goel <akash.goel@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://lkml.kernel.org/r/1470909140-25919-1-git-send-email-akash.goel@intel.com
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/include/linux/relay.h b/include/linux/relay.h
index d7c8359..eb295e3 100644
--- a/include/linux/relay.h
+++ b/include/linux/relay.h
@@ -19,6 +19,7 @@
#include <linux/fs.h>
#include <linux/poll.h>
#include <linux/kref.h>
+#include <linux/percpu.h>
/*
* Tracks changes to rchan/rchan_buf structs
@@ -63,7 +64,7 @@
struct kref kref; /* channel refcount */
void *private_data; /* for user-defined data */
size_t last_toobig; /* tried to log event > subbuf size */
- struct rchan_buf *buf[NR_CPUS]; /* per-cpu channel buffers */
+ struct rchan_buf ** __percpu buf; /* per-cpu channel buffers */
int is_global; /* One global buffer ? */
struct list_head list; /* for channel list */
struct dentry *parent; /* parent dentry passed to open */
@@ -204,7 +205,7 @@
struct rchan_buf *buf;
local_irq_save(flags);
- buf = chan->buf[smp_processor_id()];
+ buf = *this_cpu_ptr(chan->buf);
if (unlikely(buf->offset + length > chan->subbuf_size))
length = relay_switch_subbuf(buf, length);
memcpy(buf->data + buf->offset, data, length);
@@ -230,12 +231,12 @@
{
struct rchan_buf *buf;
- buf = chan->buf[get_cpu()];
+ buf = *get_cpu_ptr(chan->buf);
if (unlikely(buf->offset + length > buf->chan->subbuf_size))
length = relay_switch_subbuf(buf, length);
memcpy(buf->data + buf->offset, data, length);
buf->offset += length;
- put_cpu();
+ put_cpu_ptr(chan->buf);
}
/**
@@ -251,17 +252,19 @@
*/
static inline void *relay_reserve(struct rchan *chan, size_t length)
{
- void *reserved;
- struct rchan_buf *buf = chan->buf[smp_processor_id()];
+ void *reserved = NULL;
+ struct rchan_buf *buf = *get_cpu_ptr(chan->buf);
if (unlikely(buf->offset + length > buf->chan->subbuf_size)) {
length = relay_switch_subbuf(buf, length);
if (!length)
- return NULL;
+ goto end;
}
reserved = buf->data + buf->offset;
buf->offset += length;
+end:
+ put_cpu_ptr(chan->buf);
return reserved;
}