#ifndef _LTTNG_RING_BUFFER_FRONTEND_INTERNAL_H

#define _LTTNG_RING_BUFFER_FRONTEND_INTERNAL_H

/*

 * libringbuffer/frontend_internal.h

 *

 * Ring Buffer Library Synchronization Header (internal helpers).

 *

 * Copyright (C) 2005-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

 *

 * This library is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; only

 * version 2.1 of the License.

 *

 * This library is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with this library; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

 *

 *

 * Author:

 *	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

 *

 * See ring_buffer_frontend.c for more information on wait-free algorithms.

 *

 * Dual LGPL v2.1/GPL v2 license.

 */

#include <urcu/compiler.h>

#include <urcu/tls-compat.h>

#include <signal.h>

#include <pthread.h>

#include <lttng/ringbuffer-config.h>

#include "backend_types.h"

#include "frontend_types.h"

#include "shm.h"

/* Buffer offset macros */

/* buf_trunc mask selects only the buffer number. */

static inline

unsigned long buf_trunc(unsigned long offset, struct channel *chan)

{

	return offset & ~(chan->backend.buf_size - 1);

}

/* Select the buffer number value (counter). */

static inline

unsigned long buf_trunc_val(unsigned long offset, struct channel *chan)

{

	return buf_trunc(offset, chan) >> chan->backend.buf_size_order;

}

/* buf_offset mask selects only the offset within the current buffer. */

static inline

unsigned long buf_offset(unsigned long offset, struct channel *chan)

{

	return offset & (chan->backend.buf_size - 1);

}

/* subbuf_offset mask selects the offset within the current subbuffer. */

static inline

unsigned long subbuf_offset(unsigned long offset, struct channel *chan)

{

	return offset & (chan->backend.subbuf_size - 1);

}

/* subbuf_trunc mask selects the subbuffer number. */

static inline

unsigned long subbuf_trunc(unsigned long offset, struct channel *chan)

{

	return offset & ~(chan->backend.subbuf_size - 1);

}

/* subbuf_align aligns the offset to the next subbuffer. */

static inline

unsigned long subbuf_align(unsigned long offset, struct channel *chan)

{

	return (offset + chan->backend.subbuf_size)

	       & ~(chan->backend.subbuf_size - 1);

}

/* subbuf_index returns the index of the current subbuffer within the buffer. */

static inline

unsigned long subbuf_index(unsigned long offset, struct channel *chan)

{

	return buf_offset(offset, chan) >> chan->backend.subbuf_size_order;

}

/*

 * Last TSC comparison functions. Check if the current TSC overflows tsc_bits

 * bits from the last TSC read. When overflows are detected, the full 64-bit

 * timestamp counter should be written in the record header. Reads and writes

 * last_tsc atomically.

 */

#if (CAA_BITS_PER_LONG == 32)

static inline

void save_last_tsc(const struct lttng_ust_lib_ring_buffer_config *config,

		   struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc)

{

	if (config->tsc_bits == 0 || config->tsc_bits == 64)

		return;

	/*

	 * Ensure the compiler performs this update in a single instruction.

	 */

	v_set(config, &buf->last_tsc, (unsigned long)(tsc >> config->tsc_bits));

}

static inline

int last_tsc_overflow(const struct lttng_ust_lib_ring_buffer_config *config,

		      struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc)

{

	unsigned long tsc_shifted;

	if (config->tsc_bits == 0 || config->tsc_bits == 64)

		return 0;

	tsc_shifted = (unsigned long)(tsc >> config->tsc_bits);

	if (caa_unlikely(tsc_shifted

		     - (unsigned long)v_read(config, &buf->last_tsc)))

		return 1;

	else

		return 0;

}

#else

static inline

void save_last_tsc(const struct lttng_ust_lib_ring_buffer_config *config,

		   struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc)

{

	if (config->tsc_bits == 0 || config->tsc_bits == 64)

		return;

	v_set(config, &buf->last_tsc, (unsigned long)tsc);

}

static inline

int last_tsc_overflow(const struct lttng_ust_lib_ring_buffer_config *config,

		      struct lttng_ust_lib_ring_buffer *buf, uint64_t tsc)

{

	if (config->tsc_bits == 0 || config->tsc_bits == 64)

		return 0;

	if (caa_unlikely((tsc - v_read(config, &buf->last_tsc))

		     >> config->tsc_bits))

		return 1;

	else

		return 0;

}

#endif

extern

int lib_ring_buffer_reserve_slow(struct lttng_ust_lib_ring_buffer_ctx *ctx);

extern

void lib_ring_buffer_switch_slow(struct lttng_ust_lib_ring_buffer *buf,

				 enum switch_mode mode,

				 struct lttng_ust_shm_handle *handle);

/* Buffer write helpers */

static inline

void lib_ring_buffer_reserve_push_reader(struct lttng_ust_lib_ring_buffer *buf,

					 struct channel *chan,

					 unsigned long offset)

{

	unsigned long consumed_old, consumed_new;

	do {

		consumed_old = uatomic_read(&buf->consumed);

		/*

		 * If buffer is in overwrite mode, push the reader consumed

		 * count if the write position has reached it and we are not

		 * at the first iteration (don't push the reader farther than

		 * the writer). This operation can be done concurrently by many

		 * writers in the same buffer, the writer being at the farthest

		 * write position sub-buffer index in the buffer being the one

		 * which will win this loop.

		 */

		if (caa_unlikely(subbuf_trunc(offset, chan)

			      - subbuf_trunc(consumed_old, chan)

			     >= chan->backend.buf_size))

			consumed_new = subbuf_align(consumed_old, chan);

		else

			return;

	} while (caa_unlikely(uatomic_cmpxchg(&buf->consumed, consumed_old,

					      consumed_new) != consumed_old));

}

static inline

void lib_ring_buffer_vmcore_check_deliver(const struct lttng_ust_lib_ring_buffer_config *config,

					  struct lttng_ust_lib_ring_buffer *buf,

				          unsigned long commit_count,

				          unsigned long idx,

					  struct lttng_ust_shm_handle *handle)

{

	if (config->oops == RING_BUFFER_OOPS_CONSISTENCY)

		v_set(config, &shmp_index(handle, buf->commit_hot, idx)->seq, commit_count);

}

static inline

int lib_ring_buffer_poll_deliver(const struct lttng_ust_lib_ring_buffer_config *config,

				 struct lttng_ust_lib_ring_buffer *buf,

			         struct channel *chan,

				 struct lttng_ust_shm_handle *handle)

{

	unsigned long consumed_old, consumed_idx, commit_count, write_offset;

	consumed_old = uatomic_read(&buf->consumed);

	consumed_idx = subbuf_index(consumed_old, chan);

	commit_count = v_read(config, &shmp_index(handle, buf->commit_cold, consumed_idx)->cc_sb);

	/*

	 * No memory barrier here, since we are only interested

	 * in a statistically correct polling result. The next poll will

	 * get the data is we are racing. The mb() that ensures correct

	 * memory order is in get_subbuf.

	 */

	write_offset = v_read(config, &buf->offset);

	/*

	 * Check that the subbuffer we are trying to consume has been

	 * already fully committed.

	 */

	if (((commit_count - chan->backend.subbuf_size)

	     & chan->commit_count_mask)

	    - (buf_trunc(consumed_old, chan)

	       >> chan->backend.num_subbuf_order)

	    != 0)

		return 0;

	/*

	 * Check that we are not about to read the same subbuffer in

	 * which the writer head is.

	 */

	if (subbuf_trunc(write_offset, chan) - subbuf_trunc(consumed_old, chan)

	    == 0)

		return 0;

	return 1;

}

static inline

int lib_ring_buffer_pending_data(const struct lttng_ust_lib_ring_buffer_config *config,

				 struct lttng_ust_lib_ring_buffer *buf,

				 struct channel *chan)

{

	return !!subbuf_offset(v_read(config, &buf->offset), chan);

}

static inline

unsigned long lib_ring_buffer_get_data_size(const struct lttng_ust_lib_ring_buffer_config *config,

					    struct lttng_ust_lib_ring_buffer *buf,

					    unsigned long idx,

					    struct lttng_ust_shm_handle *handle)

{

	return subbuffer_get_data_size(config, &buf->backend, idx, handle);

}

/*

 * Check if all space reservation in a buffer have been committed. This helps

 * knowing if an execution context is nested (for per-cpu buffers only).

 * This is a very specific ftrace use-case, so we keep this as "internal" API.

 */

static inline

int lib_ring_buffer_reserve_committed(const struct lttng_ust_lib_ring_buffer_config *config,

				      struct lttng_ust_lib_ring_buffer *buf,

				      struct channel *chan,

				      struct lttng_ust_shm_handle *handle)

{

	unsigned long offset, idx, commit_count;

	CHAN_WARN_ON(chan, config->alloc != RING_BUFFER_ALLOC_PER_CPU);

	CHAN_WARN_ON(chan, config->sync != RING_BUFFER_SYNC_PER_CPU);

	/*

	 * Read offset and commit count in a loop so they are both read

	 * atomically wrt interrupts. By deal with interrupt concurrency by

	 * restarting both reads if the offset has been pushed. Note that given

	 * we only have to deal with interrupt concurrency here, an interrupt

	 * modifying the commit count will also modify "offset", so it is safe

	 * to only check for offset modifications.

	 */

	do {

		offset = v_read(config, &buf->offset);

		idx = subbuf_index(offset, chan);

		commit_count = v_read(config, &shmp_index(handle, buf->commit_hot, idx)->cc);

	} while (offset != v_read(config, &buf->offset));

	return ((buf_trunc(offset, chan) >> chan->backend.num_subbuf_order)

		     - (commit_count & chan->commit_count_mask) == 0);

}

static inline

void lib_ring_buffer_wakeup(struct lttng_ust_lib_ring_buffer *buf,

		struct lttng_ust_shm_handle *handle)

{

	int wakeup_fd = shm_get_wakeup_fd(handle, &buf->self._ref);

	sigset_t sigpipe_set, pending_set, old_set;

	int ret, sigpipe_was_pending = 0;

	if (wakeup_fd < 0)

		return;

	/*

	 * Wake-up the other end by writing a null byte in the pipe

	 * (non-blocking).  Important note: Because writing into the

	 * pipe is non-blocking (and therefore we allow dropping wakeup

	 * data, as long as there is wakeup data present in the pipe

	 * buffer to wake up the consumer), the consumer should perform

	 * the following sequence for waiting:

	 * 1) empty the pipe (reads).

	 * 2) check if there is data in the buffer.

	 * 3) wait on the pipe (poll).

	 *

	 * Discard the SIGPIPE from write(), not disturbing any SIGPIPE

	 * that might be already pending. If a bogus SIGPIPE is sent to

	 * the entire process concurrently by a malicious user, it may

	 * be simply discarded.

	 */

	ret = sigemptyset(&pending_set);

	assert(!ret);

	/*

	 * sigpending returns the mask of signals that are _both_

	 * blocked for the thread _and_ pending for either the thread or

	 * the entire process.

	 */

	ret = sigpending(&pending_set);

	assert(!ret);

	sigpipe_was_pending = sigismember(&pending_set, SIGPIPE);

	/*

	 * If sigpipe was pending, it means it was already blocked, so

	 * no need to block it.

	 */

	if (!sigpipe_was_pending) {

		ret = sigemptyset(&sigpipe_set);

		assert(!ret);

		ret = sigaddset(&sigpipe_set, SIGPIPE);

		assert(!ret);

		ret = pthread_sigmask(SIG_BLOCK, &sigpipe_set, &old_set);

		assert(!ret);

	}

	do {

		ret = write(wakeup_fd, "", 1);

	} while (ret == -1L && errno == EINTR);

	if (ret == -1L && errno == EPIPE && !sigpipe_was_pending) {

		struct timespec timeout = { 0, 0 };

		do {

			ret = sigtimedwait(&sigpipe_set, NULL,

				&timeout);

		} while (ret == -1L && errno == EINTR);

	}

	if (!sigpipe_was_pending) {

		ret = pthread_sigmask(SIG_SETMASK, &old_set, NULL);

		assert(!ret);

	}

}

/*

 * Receive end of subbuffer TSC as parameter. It has been read in the

 * space reservation loop of either reserve or switch, which ensures it

 * progresses monotonically with event records in the buffer. Therefore,

 * it ensures that the end timestamp of a subbuffer is <= begin

 * timestamp of the following subbuffers.

 */

static inline

void lib_ring_buffer_check_deliver(const struct lttng_ust_lib_ring_buffer_config *config,

				   struct lttng_ust_lib_ring_buffer *buf,

			           struct channel *chan,

			           unsigned long offset,

				   unsigned long commit_count,

			           unsigned long idx,

				   struct lttng_ust_shm_handle *handle,

				   uint64_t tsc)

{

	unsigned long old_commit_count = commit_count

					 - chan->backend.subbuf_size;

	/* Check if all commits have been done */

	if (caa_unlikely((buf_trunc(offset, chan) >> chan->backend.num_subbuf_order)

		     - (old_commit_count & chan->commit_count_mask) == 0)) {

		/*

		 * If we succeeded at updating cc_sb below, we are the subbuffer

		 * writer delivering the subbuffer. Deals with concurrent

		 * updates of the "cc" value without adding a add_return atomic

		 * operation to the fast path.

		 *

		 * We are doing the delivery in two steps:

		 * - First, we cmpxchg() cc_sb to the new value

		 *   old_commit_count + 1. This ensures that we are the only

		 *   subbuffer user successfully filling the subbuffer, but we

		 *   do _not_ set the cc_sb value to "commit_count" yet.

		 *   Therefore, other writers that would wrap around the ring

		 *   buffer and try to start writing to our subbuffer would

		 *   have to drop records, because it would appear as

		 *   non-filled.

		 *   We therefore have exclusive access to the subbuffer control

		 *   structures.  This mutual exclusion with other writers is

		 *   crucially important to perform record overruns count in

		 *   flight recorder mode locklessly.

		 * - When we are ready to release the subbuffer (either for

		 *   reading or for overrun by other writers), we simply set the

		 *   cc_sb value to "commit_count" and perform delivery.

		 *

		 * The subbuffer size is least 2 bytes (minimum size: 1 page).

		 * This guarantees that old_commit_count + 1 != commit_count.

		 */

		/*

		 * Order prior updates to reserve count prior to the

		 * commit_cold cc_sb update.

		 */

		cmm_smp_wmb();

		if (caa_likely(v_cmpxchg(config, &shmp_index(handle, buf->commit_cold, idx)->cc_sb,

					 old_commit_count, old_commit_count + 1)

			   == old_commit_count)) {

			/*

			 * Start of exclusive subbuffer access. We are

			 * guaranteed to be the last writer in this subbuffer

			 * and any other writer trying to access this subbuffer

			 * in this state is required to drop records.

			 */

			v_add(config,

			      subbuffer_get_records_count(config,

							  &buf->backend,

							  idx, handle),

			      &buf->records_count);

			v_add(config,

			      subbuffer_count_records_overrun(config,

							      &buf->backend,

							      idx, handle),

			      &buf->records_overrun);

			config->cb.buffer_end(buf, tsc, idx,

					      lib_ring_buffer_get_data_size(config,

									buf,

									idx,

									handle),

					      handle);

			/*

			 * Increment the packet counter while we have exclusive

			 * access.

			 */

			subbuffer_inc_packet_count(config, &buf->backend, idx, handle);

			/*

			 * Set noref flag and offset for this subbuffer id.

			 * Contains a memory barrier that ensures counter stores

			 * are ordered before set noref and offset.

			 */

			lib_ring_buffer_set_noref_offset(config, &buf->backend, idx,

							 buf_trunc_val(offset, chan), handle);

			/*

			 * Order set_noref and record counter updates before the

			 * end of subbuffer exclusive access. Orders with

			 * respect to writers coming into the subbuffer after

			 * wrap around, and also order wrt concurrent readers.

			 */

			cmm_smp_mb();

			/* End of exclusive subbuffer access */

			v_set(config, &shmp_index(handle, buf->commit_cold, idx)->cc_sb,

			      commit_count);

			/*

			 * Order later updates to reserve count after

			 * the commit cold cc_sb update.

			 */

			cmm_smp_wmb();

			lib_ring_buffer_vmcore_check_deliver(config, buf,

						 commit_count, idx, handle);

			/*

			 * RING_BUFFER_WAKEUP_BY_WRITER wakeup is not lock-free.

			 */

			if (config->wakeup == RING_BUFFER_WAKEUP_BY_WRITER

			    && uatomic_read(&buf->active_readers)

			    && lib_ring_buffer_poll_deliver(config, buf, chan, handle)) {

				lib_ring_buffer_wakeup(buf, handle);

			}

		}

	}

}

/*

 * lib_ring_buffer_write_commit_counter

 *

 * For flight recording. must be called after commit.

 * This function increments the subbuffer's commit_seq counter each time the

 * commit count reaches back the reserve offset (modulo subbuffer size). It is

 * useful for crash dump.

 */

static inline

void lib_ring_buffer_write_commit_counter(const struct lttng_ust_lib_ring_buffer_config *config,

					  struct lttng_ust_lib_ring_buffer *buf,

				          struct channel *chan,

				          unsigned long idx,

				          unsigned long buf_offset,

				          unsigned long commit_count,

					  struct lttng_ust_shm_handle *handle)

{

	unsigned long commit_seq_old;

	if (config->oops != RING_BUFFER_OOPS_CONSISTENCY)

		return;

	/*

	 * subbuf_offset includes commit_count_mask. We can simply

	 * compare the offsets within the subbuffer without caring about

	 * buffer full/empty mismatch because offset is never zero here

	 * (subbuffer header and record headers have non-zero length).

	 */

	if (caa_unlikely(subbuf_offset(buf_offset - commit_count, chan)))

		return;

	commit_seq_old = v_read(config, &shmp_index(handle, buf->commit_hot, idx)->seq);

	while ((long) (commit_seq_old - commit_count) < 0)

		commit_seq_old = v_cmpxchg(config, &shmp_index(handle, buf->commit_hot, idx)->seq,

					   commit_seq_old, commit_count);

}

extern int lib_ring_buffer_create(struct lttng_ust_lib_ring_buffer *buf,

				  struct channel_backend *chanb, int cpu,

				  struct lttng_ust_shm_handle *handle,

				  struct shm_object *shmobj);

extern void lib_ring_buffer_free(struct lttng_ust_lib_ring_buffer *buf,

				 struct lttng_ust_shm_handle *handle);

/* Keep track of trap nesting inside ring buffer code */

extern DECLARE_URCU_TLS(unsigned int, lib_ring_buffer_nesting);

#endif /* _LTTNG_RING_BUFFER_FRONTEND_INTERNAL_H */