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/* IBM_PROLOG_BEGIN_TAG */
/* This is an automatically generated prolog. */
/* */
/* $Source: src/usr/trace/buffer.H $ */
/* */
/* IBM CONFIDENTIAL */
/* */
/* COPYRIGHT International Business Machines Corp. 2012 */
/* */
/* p1 */
/* */
/* Object Code Only (OCO) source materials */
/* Licensed Internal Code Source Materials */
/* IBM HostBoot Licensed Internal Code */
/* */
/* The source code for this program is not published or otherwise */
/* divested of its trade secrets, irrespective of what has been */
/* deposited with the U.S. Copyright Office. */
/* */
/* Origin: 30 */
/* */
/* IBM_PROLOG_END_TAG */
#ifndef __TRACE_BUFFER_H
#define __TRACE_BUFFER_H
/** @file buffer.H
* Declarations for the buffer class.
*/
#include <trace/interface.H>
#include <sys/sync.h>
namespace TRACEDAEMON { class Daemon; } // Forward declaration.
namespace TRACE
{
// Forward declarations.
class BufferPage;
class Entry;
class DaemonIf;
/** @class Buffer
* @brief Class to manage the front-side (client) buffers
*
* Provides interfaces for getting an entry to write trace data to and
* committing that entry as well as extracting the component trace.
*
* Private interfaces for the daemon to ensure lockless ordering is
* maintained.
*/
class Buffer
{
public:
enum
{
/** Used as a parameter to the constructor to indicate that
* the buffer should never block (and could instead run
* the system out of memory). */
UNLIMITED = UINT32_MAX
};
/** Constructor.
*
* @param[in] i_daemon - Daemon interface for this buffer.
* @param[in] i_maxPages - Maximum number of pages to consume
* before 'claimEntry' blocks.
*/
Buffer(DaemonIf* i_daemon, size_t i_maxPages = 4);
/** @brief Claim an entry from the buffer to write data to.
*
* @param[in] i_comp - Component which will own entry.
* @param[in] i_size - Size of data portion of entry.
*
* @return An entry to write to.
*
* If pages allocated is at max pages and there is no room to
* create an entry, this function may block. For components
* which cannot block, it is expected that the buffer will be
* constructed large enough that we run out of memory before
* we block.
*/
Entry* claimEntry(ComponentDesc* i_comp, size_t i_size);
/** @brief Commit entry to buffer and component linked-list.
*
* @param[in] i_entry - Entry to commit.
*/
void commitEntry(Entry* i_entry);
/** @brief Extract component trace.
*
* See service::getBuffer. Defined here due to lockless ordering
* needs.
*/
size_t getTrace(ComponentDesc* i_comp, void* o_data, size_t i_size);
private:
volatile uint64_t iv_pagesAlloc; //< Number of pages allocated.
uint64_t iv_pagesMax; //< Maximum pages allowed.
BufferPage* volatile iv_firstPage; //< Most recent page.
/** @union locklessCounter
*
* This class is mostly lockless in that multiple trace entries
* can be created at the same time along with buffer extraction.
* This means that all client operations are lockless.
*
* There are minor operations that the daemon must do to ensure
* that a client is not in the middle of another operation, such
* as when the daemon removes the pages from the front-end to
* merge them into the backend. During this time, the daemon
* will obtain the equivalent of a write-lock, which will block
* all clients.
*
* It is required that all times where the write-lock is held
* are short and cannot cause page-faults that might deadlock
* components such as VFS and PNOR. This means that all code
* inside the write-lock is in the base image.
*
* This read/write lock is modeled here as "producers" (clients)
* and a "consumer" (daemon). The active counts of each are
* recorded with this structure and unioned to a single uint64_t
* so that they can be atomically updated as one entity.
*/
union locklessCounter
{
struct
{
uint32_t producerCount;
uint32_t consumerCount;
};
uint64_t totals;
};
locklessCounter iv_counters; //< The producer/consumer counts.
DaemonIf* iv_daemon; //< Daemon interface.
/** @brief Claim front-side buffer pages to be merged into the
* common buffer.
*
* @return Pointer to the first page (most recent) from this
* buffer.
*
* Gives ownership of all the current pages to the caller and
* resets this buffer's allocated page counts.
*/
BufferPage* claimPages();
/** @brief Perform operations with the consumer lock held.
*
* These operations cannot be done in the daemon code directly
* because the daemon code is swappable and we cannot block
* producers.
*
* This function gives a set of primatives to the daemon to
* manipulate Entry pointers while secured under the consumer lock.
*
* The primatives that can be done are:
* 1) if (condAddr == condVal) { condActAddr = condActVal }
* 2) addr = val
*
* If any of the address parameters are NULL, their action will
* not be performed. So, just calling consumerOp() has the
* side-effect of simply toggling the consumer lock on and off.
*
* The return value indicates if primative #1 failed.
*
* @param[in] i_condAddr - The address to read for primative 1.
* @param[in] i_condVal - The value to expect for primative 1.
* @param[in] i_condActAddr - The address to store for primative 1.
* @param[in] i_condActVal - The value to store for primative 1.
*
* @param[in] i_addr - The address to store for primative 2.
* @param[in] i_val - The value to store for primative 2.
*
* @return bool - false if condAddr != condVal, true otherwise.
*/
bool consumerOp(Entry** i_condAddr = NULL, Entry* i_condVal = NULL,
Entry** i_condActAddr = NULL,
Entry* i_condActVal = NULL,
Entry** i_addr = NULL, Entry* i_val = NULL);
void _producerEnter(); //< Enter client section.
void _producerExit(); //< Exit client section.
void _consumerEnter(); //< Enter daemon section.
void _consumerExit(); //< Exit daemon section.
friend class BufferTest;
friend class TRACEDAEMON::Daemon;
};
}
#endif
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