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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>
This commit is contained in:
Akash Goel
Thomas Gleixner
parent
ee1e714b94
commit
017c59c042
@ -19,6 +19,7 @@
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#include <linux/fs.h>
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#include <linux/poll.h>
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#include <linux/kref.h>
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#include <linux/percpu.h>
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/*
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* Tracks changes to rchan/rchan_buf structs
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@ -63,7 +64,7 @@ struct rchan
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struct kref kref; /* channel refcount */
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void *private_data; /* for user-defined data */
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size_t last_toobig; /* tried to log event > subbuf size */
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struct rchan_buf *buf[NR_CPUS]; /* per-cpu channel buffers */
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struct rchan_buf ** __percpu buf; /* per-cpu channel buffers */
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int is_global; /* One global buffer ? */
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struct list_head list; /* for channel list */
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struct dentry *parent; /* parent dentry passed to open */
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@ -204,7 +205,7 @@ static inline void relay_write(struct rchan *chan,
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struct rchan_buf *buf;
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local_irq_save(flags);
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buf = chan->buf[smp_processor_id()];
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buf = *this_cpu_ptr(chan->buf);
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if (unlikely(buf->offset + length > chan->subbuf_size))
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length = relay_switch_subbuf(buf, length);
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memcpy(buf->data + buf->offset, data, length);
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@ -230,12 +231,12 @@ static inline void __relay_write(struct rchan *chan,
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{
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struct rchan_buf *buf;
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buf = chan->buf[get_cpu()];
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buf = *get_cpu_ptr(chan->buf);
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if (unlikely(buf->offset + length > buf->chan->subbuf_size))
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length = relay_switch_subbuf(buf, length);
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memcpy(buf->data + buf->offset, data, length);
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buf->offset += length;
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put_cpu();
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put_cpu_ptr(chan->buf);
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}
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/**
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@ -251,17 +252,19 @@ static inline void __relay_write(struct rchan *chan,
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*/
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static inline void *relay_reserve(struct rchan *chan, size_t length)
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{
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void *reserved;
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struct rchan_buf *buf = chan->buf[smp_processor_id()];
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void *reserved = NULL;
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struct rchan_buf *buf = *get_cpu_ptr(chan->buf);
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if (unlikely(buf->offset + length > buf->chan->subbuf_size)) {
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length = relay_switch_subbuf(buf, length);
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if (!length)
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return NULL;
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goto end;
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}
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reserved = buf->data + buf->offset;
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buf->offset += length;
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end:
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put_cpu_ptr(chan->buf);
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return reserved;
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}
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@ -214,7 +214,7 @@ static void relay_destroy_buf(struct rchan_buf *buf)
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__free_page(buf->page_array[i]);
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relay_free_page_array(buf->page_array);
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}
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chan->buf[buf->cpu] = NULL;
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*per_cpu_ptr(chan->buf, buf->cpu) = NULL;
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kfree(buf->padding);
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kfree(buf);
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kref_put(&chan->kref, relay_destroy_channel);
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@ -382,20 +382,21 @@ static void __relay_reset(struct rchan_buf *buf, unsigned int init)
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*/
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void relay_reset(struct rchan *chan)
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{
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struct rchan_buf *buf;
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unsigned int i;
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if (!chan)
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return;
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if (chan->is_global && chan->buf[0]) {
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__relay_reset(chan->buf[0], 0);
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if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0))) {
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__relay_reset(buf, 0);
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return;
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}
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mutex_lock(&relay_channels_mutex);
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for_each_possible_cpu(i)
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if (chan->buf[i])
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__relay_reset(chan->buf[i], 0);
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if ((buf = *per_cpu_ptr(chan->buf, i)))
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__relay_reset(buf, 0);
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mutex_unlock(&relay_channels_mutex);
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}
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EXPORT_SYMBOL_GPL(relay_reset);
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@ -440,7 +441,7 @@ static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu)
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struct dentry *dentry;
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if (chan->is_global)
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return chan->buf[0];
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return *per_cpu_ptr(chan->buf, 0);
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buf = relay_create_buf(chan);
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if (!buf)
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@ -464,7 +465,7 @@ static struct rchan_buf *relay_open_buf(struct rchan *chan, unsigned int cpu)
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__relay_reset(buf, 1);
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if(chan->is_global) {
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chan->buf[0] = buf;
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*per_cpu_ptr(chan->buf, 0) = buf;
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buf->cpu = 0;
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}
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@ -526,22 +527,24 @@ static int relay_hotcpu_callback(struct notifier_block *nb,
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{
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unsigned int hotcpu = (unsigned long)hcpu;
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struct rchan *chan;
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struct rchan_buf *buf;
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switch(action) {
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case CPU_UP_PREPARE:
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case CPU_UP_PREPARE_FROZEN:
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mutex_lock(&relay_channels_mutex);
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list_for_each_entry(chan, &relay_channels, list) {
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if (chan->buf[hotcpu])
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if ((buf = *per_cpu_ptr(chan->buf, hotcpu)))
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continue;
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chan->buf[hotcpu] = relay_open_buf(chan, hotcpu);
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if(!chan->buf[hotcpu]) {
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buf = relay_open_buf(chan, hotcpu);
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if (!buf) {
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printk(KERN_ERR
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"relay_hotcpu_callback: cpu %d buffer "
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"creation failed\n", hotcpu);
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mutex_unlock(&relay_channels_mutex);
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return notifier_from_errno(-ENOMEM);
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}
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*per_cpu_ptr(chan->buf, hotcpu) = buf;
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}
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mutex_unlock(&relay_channels_mutex);
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break;
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@ -583,6 +586,7 @@ struct rchan *relay_open(const char *base_filename,
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{
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unsigned int i;
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struct rchan *chan;
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struct rchan_buf *buf;
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if (!(subbuf_size && n_subbufs))
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return NULL;
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@ -593,6 +597,7 @@ struct rchan *relay_open(const char *base_filename,
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if (!chan)
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return NULL;
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chan->buf = alloc_percpu(struct rchan_buf *);
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chan->version = RELAYFS_CHANNEL_VERSION;
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chan->n_subbufs = n_subbufs;
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chan->subbuf_size = subbuf_size;
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@ -608,9 +613,10 @@ struct rchan *relay_open(const char *base_filename,
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mutex_lock(&relay_channels_mutex);
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for_each_online_cpu(i) {
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chan->buf[i] = relay_open_buf(chan, i);
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if (!chan->buf[i])
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buf = relay_open_buf(chan, i);
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if (!buf)
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goto free_bufs;
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*per_cpu_ptr(chan->buf, i) = buf;
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}
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list_add(&chan->list, &relay_channels);
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mutex_unlock(&relay_channels_mutex);
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@ -619,8 +625,8 @@ struct rchan *relay_open(const char *base_filename,
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free_bufs:
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for_each_possible_cpu(i) {
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if (chan->buf[i])
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relay_close_buf(chan->buf[i]);
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if ((buf = *per_cpu_ptr(chan->buf, i)))
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relay_close_buf(buf);
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}
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kref_put(&chan->kref, relay_destroy_channel);
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@ -666,6 +672,7 @@ int relay_late_setup_files(struct rchan *chan,
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unsigned int i, curr_cpu;
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unsigned long flags;
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struct dentry *dentry;
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struct rchan_buf *buf;
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struct rchan_percpu_buf_dispatcher disp;
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if (!chan || !base_filename)
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@ -684,10 +691,11 @@ int relay_late_setup_files(struct rchan *chan,
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if (chan->is_global) {
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err = -EINVAL;
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if (!WARN_ON_ONCE(!chan->buf[0])) {
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dentry = relay_create_buf_file(chan, chan->buf[0], 0);
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buf = *per_cpu_ptr(chan->buf, 0);
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if (!WARN_ON_ONCE(!buf)) {
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dentry = relay_create_buf_file(chan, buf, 0);
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if (dentry && !WARN_ON_ONCE(!chan->is_global)) {
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relay_set_buf_dentry(chan->buf[0], dentry);
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relay_set_buf_dentry(buf, dentry);
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err = 0;
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}
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}
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@ -702,13 +710,14 @@ int relay_late_setup_files(struct rchan *chan,
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* on all currently online CPUs.
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*/
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for_each_online_cpu(i) {
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if (unlikely(!chan->buf[i])) {
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buf = *per_cpu_ptr(chan->buf, i);
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if (unlikely(!buf)) {
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WARN_ONCE(1, KERN_ERR "CPU has no buffer!\n");
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err = -EINVAL;
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break;
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}
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dentry = relay_create_buf_file(chan, chan->buf[i], i);
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dentry = relay_create_buf_file(chan, buf, i);
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if (unlikely(!dentry)) {
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err = -EINVAL;
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break;
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@ -716,10 +725,10 @@ int relay_late_setup_files(struct rchan *chan,
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if (curr_cpu == i) {
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local_irq_save(flags);
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relay_set_buf_dentry(chan->buf[i], dentry);
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relay_set_buf_dentry(buf, dentry);
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local_irq_restore(flags);
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} else {
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disp.buf = chan->buf[i];
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disp.buf = buf;
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disp.dentry = dentry;
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smp_mb();
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/* relay_channels_mutex must be held, so wait. */
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@ -822,11 +831,10 @@ void relay_subbufs_consumed(struct rchan *chan,
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if (!chan)
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return;
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if (cpu >= NR_CPUS || !chan->buf[cpu] ||
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subbufs_consumed > chan->n_subbufs)
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buf = *per_cpu_ptr(chan->buf, cpu);
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if (cpu >= NR_CPUS || !buf || subbufs_consumed > chan->n_subbufs)
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return;
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buf = chan->buf[cpu];
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if (subbufs_consumed > buf->subbufs_produced - buf->subbufs_consumed)
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buf->subbufs_consumed = buf->subbufs_produced;
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else
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@ -842,18 +850,19 @@ EXPORT_SYMBOL_GPL(relay_subbufs_consumed);
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*/
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void relay_close(struct rchan *chan)
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{
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struct rchan_buf *buf;
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unsigned int i;
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if (!chan)
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return;
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mutex_lock(&relay_channels_mutex);
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if (chan->is_global && chan->buf[0])
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relay_close_buf(chan->buf[0]);
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if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0)))
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relay_close_buf(buf);
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else
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for_each_possible_cpu(i)
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if (chan->buf[i])
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relay_close_buf(chan->buf[i]);
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if ((buf = *per_cpu_ptr(chan->buf, i)))
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relay_close_buf(buf);
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if (chan->last_toobig)
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printk(KERN_WARNING "relay: one or more items not logged "
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@ -874,20 +883,21 @@ EXPORT_SYMBOL_GPL(relay_close);
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*/
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void relay_flush(struct rchan *chan)
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{
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struct rchan_buf *buf;
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unsigned int i;
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if (!chan)
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return;
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if (chan->is_global && chan->buf[0]) {
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relay_switch_subbuf(chan->buf[0], 0);
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if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0))) {
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relay_switch_subbuf(buf, 0);
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return;
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}
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mutex_lock(&relay_channels_mutex);
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for_each_possible_cpu(i)
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if (chan->buf[i])
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relay_switch_subbuf(chan->buf[i], 0);
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if ((buf = *per_cpu_ptr(chan->buf, i)))
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relay_switch_subbuf(buf, 0);
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mutex_unlock(&relay_channels_mutex);
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}
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EXPORT_SYMBOL_GPL(relay_flush);
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