src/xcalls/x_read_pipe.c

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#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>
#include <misc/debug.h>
#include <misc/errno.h>
#include <misc/generic_types.h>
#include <core/tx.h>
#include <core/config.h>
#include <core/koa.h>
#include <core/buffer.h>
#include <core/stats.h>
#include <libc/syscalls.h>
#include <core/txdesc.h>
#include <xcalls/xcalls.h>


typedef struct x_read_pipe_commit_undo_args_s x_read_pipe_commit_undo_args_t;

struct x_read_pipe_commit_undo_args_s {
        txc_koa_t             *koa;
        txc_buffer_circular_t *buffer;
};


static
void 
x_read_pipe_undo(void *args, int *result) 
{
        x_read_pipe_commit_undo_args_t *args_undo = (x_read_pipe_commit_undo_args_t *) args;
        int                            local_result = 0;

        args_undo->buffer->state = TXC_BUFFER_STATE_NON_SPECULATIVE;
        if (result) {
                *result = local_result;
        }
}


static 
void
x_read_pipe_commit(void *args, int *result)
{
        x_read_pipe_commit_undo_args_t *args_commit = (x_read_pipe_commit_undo_args_t *) args;
        int                            local_result = 0;
        txc_buffer_circular_t          *buffer;

        buffer = args_commit->buffer;

        if (buffer->speculative_primary_tail != buffer->speculative_primary_head) {
                buffer->primary_head = buffer->speculative_primary_head; 
                buffer->primary_tail = buffer->speculative_primary_tail; 
        } else if (buffer->speculative_secondary_tail != buffer->speculative_secondary_head) {
                buffer->primary_head = buffer->speculative_secondary_head; 
                buffer->primary_tail = buffer->speculative_secondary_tail; 
                buffer->secondary_head = buffer->secondary_tail = 0;
        } else {
                buffer->primary_head = buffer->primary_tail = 0;
                buffer->secondary_head = buffer->secondary_tail = 0;
        }
        buffer->state = TXC_BUFFER_STATE_NON_SPECULATIVE;
        if (result) {
                *result = local_result;
        }
}


static 
ssize_t 
__txc_read_pipe(txc_tx_t *txd, txc_bool_t speculative_read,
                int fd, void *buf, size_t nbyte, int *result) 
{
        txc_koamgr_t                   *koamgr = txc_g_koamgr;
        txc_koa_t                      *koa;
        txc_sentinel_t                 *sentinel;
        txc_result_t                   xret;
        int                            ret;
        x_read_pipe_commit_undo_args_t *args_commit_undo;
        int                            local_result = 0;
        int                            store_in_primary_buffer;
        int                            store_in_secondary_buffer;
        int                            hdr_base_index;
        int                            needed_bytes;
        txc_buffer_circular_t          *buffer;

        
        /* 
         * FIXME: We don't handle the case where we need to consume more data 
         * than available in the buffer. In such a case you need to request
         * the additional data.
         */

        txc_koa_lock_fd(koamgr, fd);
        xret = txc_koa_lookup_fd2koa(koamgr, fd, &koa);
        if (xret == TXC_R_FAILURE) {
                /* 
                 * The KOA mapped to the file descriptor has gone. Report
                 * this error as invalid file descriptor.
                 */
                txc_koa_unlock_fd(koamgr, fd);
                local_result = EBADF;
                ret = -1;
                goto done;
        }
        buffer = (txc_buffer_circular_t *) txc_koa_get_buffer(koa);

        if (!speculative_read) {
                txc_koa_unlock_fd(koamgr, fd);
                if ((buffer->primary_tail != buffer->primary_head) ||
                    (buffer->secondary_tail != buffer->secondary_head)) {
                        /* There are buffered data available */
                        if (buffer->primary_tail != buffer->primary_head) {
                                /* Consume data from the primary buffer */
                                hdr_base_index = buffer->primary_head;
                                buffer->primary_head += nbyte;
                        } else {
                                /* Consume data from the secondary buffer and make the secondary 
                                 * buffer primary 
                                 */
                                hdr_base_index = buffer->secondary_head;
                                buffer->secondary_head += nbyte;
                                buffer->primary_tail = buffer->secondary_tail; 
                                buffer->primary_head = buffer->secondary_head; 
                                buffer->secondary_head = buffer->secondary_tail = 0;
                        }
                        /* Now fall through to do the copy */
                } else { 
                        ret = txc_libc_read(fd, buf, nbyte);
                        local_result = errno;
                        goto done;
                }
        } else {
                /* READ is speculative */               
                sentinel = txc_koa_get_sentinel(koa);
                xret = txc_sentinel_tryacquire(txd, sentinel, 
                                                                           TXC_SENTINEL_ACQUIREONRETRY);
                txc_koa_unlock_fd(koamgr, fd);
                if (xret == TXC_R_BUSYSENTINEL) {
                        txc_tx_abort_transaction(txd, TXC_ABORTREASON_BUSYSENTINEL);
                        TXC_INTERNALERROR("Never gets here. Transaction abort failed.\n");
                }

                /* Got sentinel. Continue with the rest of the stuff. */
                if (buffer->state == TXC_BUFFER_STATE_NON_SPECULATIVE) {
                        if ((args_commit_undo = (x_read_pipe_commit_undo_args_t *)
                                                                         txc_buffer_linear_malloc(txd->buffer_linear, 
                                                                                                                          sizeof(x_read_pipe_commit_undo_args_t)))
                                 == NULL)
                        {
                                local_result = ENOMEM;
                                ret = -1;
                                goto done;
                        }
                        buffer->speculative_primary_head = buffer->primary_head;
                        buffer->speculative_primary_tail = buffer->primary_tail;
                        buffer->speculative_secondary_head = buffer->secondary_head;
                        buffer->speculative_secondary_tail = buffer->secondary_tail;
                        buffer->state = TXC_BUFFER_STATE_SPECULATIVE;

                        args_commit_undo->koa = koa;
                        args_commit_undo->buffer = buffer;

                        txc_tx_register_commit_action(txd, x_read_pipe_commit, 
                                                                                  (void *) args_commit_undo, result,
                                                                                  TXC_TX_REGULAR_COMMIT_ACTION_ORDER);
                        txc_tx_register_undo_action(txd, x_read_pipe_undo, 
                                                                                (void *) args_commit_undo, result,
                                                                                TXC_TX_REGULAR_UNDO_ACTION_ORDER);
                }

                if (buffer->speculative_primary_tail != buffer->speculative_primary_head ||
                                buffer->speculative_secondary_tail != buffer->speculative_secondary_head) {
                        /* There are buffered data available to consume*/
                        if (buffer->speculative_primary_tail != buffer->speculative_primary_head) {
                                /* Consume data from the primary buffer */
                                hdr_base_index = buffer->speculative_primary_head;
                                buffer->speculative_primary_head += nbyte;
                        } else {
                                /* Consume data from the secondary buffer */
                                hdr_base_index = buffer->speculative_secondary_head;
                                buffer->speculative_secondary_head += nbyte;
                        }
                        ret = nbyte;
                } else { 
                        /* No buffered data available 
                         * 1) Find space in the buffer
                         * 3) Issue a read call to the kernel to bring the data in the buffer
                         * 4) Copy the buffered data back to the application buffer
                         */
                        needed_bytes = nbyte; 
                        store_in_primary_buffer = store_in_secondary_buffer = 0;
                        if (buffer->primary_tail < (buffer->size_max - needed_bytes)) {
                                /* There is space in the primary part of the buffer */
                                hdr_base_index = buffer->primary_tail;
                                store_in_primary_buffer = 1;
                        }       else if (buffer->secondary_tail < 
                                                                                                        (buffer->primary_head + 1 - needed_bytes)) {
                                /* There is space in the secondary part of the buffer */
                                hdr_base_index = buffer->secondary_tail;
                                store_in_secondary_buffer = 1;
                        } else {
                                /* There is not space in the buffer */
                                local_result = ENOMEM;
                                ret = -1;
                                goto done;
                        }
                        ret = txc_libc_read(fd, &(buffer->buf[hdr_base_index]), nbyte);
                        if (ret > 0) {
                                if (store_in_primary_buffer) {
                                        buffer->primary_tail += ret;
                                } else if (store_in_secondary_buffer) {
                                        buffer->secondary_tail += ret;
                                } else {
                                        TXC_INTERNALERROR("Sanity check -- shouldn't come here.\n");
                                }
                        }
                        txc_stats_txstat_increment(txd, XCALL, x_read_pipe, 1);
                }
        }       
        /* Copy data from the buffer back to the application buffer */
        memcpy(buf, &buffer->buf[hdr_base_index], nbyte); 
        local_result = 0;
done:
        if (result) {
                *result = local_result;
        }
        return ret;
}


ssize_t 
XCALL_DEF(x_read_pipe)(int fd, void *buf, size_t nbyte, int *result)
{
        txc_tx_t           *txd;
        int                ret;

        txd = txc_tx_get_txd();

        switch(txc_tx_get_xactstate(txd)) {
                case TXC_XACTSTATE_TRANSACTIONAL_IRREVOCABLE:
                case TXC_XACTSTATE_NONTRANSACTIONAL:
                        ret = __txc_read_pipe(txd, TXC_BOOL_FALSE, fd, buf, nbyte, result);
                        break;
                case TXC_XACTSTATE_TRANSACTIONAL_RETRYABLE:
                        ret = __txc_read_pipe(txd, TXC_BOOL_TRUE, fd, buf, nbyte, result);
                        break;
                default:
                        TXC_INTERNALERROR("Unknown transaction state\n");
        }
        return ret;
}

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