Current File : //usr/share/systemtap/runtime/print_flush.c
/* -*- linux-c -*-
* Print Flush Function
* Copyright (C) 2007-2008 Red Hat Inc.
*
* This file is part of systemtap, and is free software. You can
* redistribute it and/or modify it under the terms of the GNU General
* Public License (GPL); either version 2, or (at your option) any
* later version.
*/
/** Send the print buffer to the transport now.
* Output accumulates in the print buffer until it
* is filled, or this is called. This MUST be called before returning
* from a probe or accumulated output in the print buffer will be lost.
*
* @note Preemption must be disabled to use this.
*/
static STP_DEFINE_SPINLOCK(_stp_print_lock);
void stp_print_flush(_stp_pbuf *pb)
{
size_t len = pb->len;
void *entry = NULL;
/* check to see if there is anything in the buffer */
if (likely(len == 0))
return;
pb->len = 0;
if (unlikely(_stp_transport_get_state() != STP_TRANSPORT_RUNNING))
return;
dbug_trans(1, "len = %zu\n", len);
#ifdef STP_BULKMODE
#ifdef NO_PERCPU_HEADERS
{
char *bufp = pb->buf;
while (len > 0) {
size_t bytes_reserved;
bytes_reserved = _stp_data_write_reserve(len, &entry);
if (likely(entry && bytes_reserved > 0)) {
memcpy(_stp_data_entry_data(entry), bufp,
bytes_reserved);
_stp_data_write_commit(entry);
bufp += bytes_reserved;
len -= bytes_reserved;
}
else {
atomic_inc(&_stp_transport_failures);
break;
}
}
}
#else /* !NO_PERCPU_HEADERS */
{
char *bufp = pb->buf;
struct _stp_trace t = { .sequence = _stp_seq_inc(),
.pdu_len = len};
size_t bytes_reserved;
bytes_reserved = _stp_data_write_reserve(sizeof(struct _stp_trace), &entry);
if (likely(entry && bytes_reserved > 0)) {
/* prevent unaligned access by using memcpy() */
memcpy(_stp_data_entry_data(entry), &t, sizeof(t));
_stp_data_write_commit(entry);
}
else {
atomic_inc(&_stp_transport_failures);
return;
}
while (len > 0) {
bytes_reserved = _stp_data_write_reserve(len, &entry);
if (likely(entry && bytes_reserved > 0)) {
memcpy(_stp_data_entry_data(entry), bufp,
bytes_reserved);
_stp_data_write_commit(entry);
bufp += bytes_reserved;
len -= bytes_reserved;
}
else {
atomic_inc(&_stp_transport_failures);
break;
}
}
}
#endif /* !NO_PERCPU_HEADERS */
#else /* !STP_BULKMODE */
#if STP_TRANSPORT_VERSION == 1
/** STP_TRANSPORT_VERSION == 1 is special, _stp_ctl_send will
pass through procfs _stp_ctl_write_fs which recognizes
STP_REALTIME_DATA as data that can be concatenated if the
previous buffer is also of type STP_REALTIME_DATA and there
is some room left in that packet instead of creating a new
packet to be queued. */
if (unlikely(_stp_ctl_send(STP_REALTIME_DATA, pb->buf, len) <= 0))
atomic_inc (&_stp_transport_failures);
#else /* STP_TRANSPORT_VERSION != 1 */
{
unsigned long flags;
struct context* __restrict__ c = NULL;
char *bufp = pb->buf;
/* Prevent probe reentrancy on _stp_print_lock.
*
* Since stp_print_flush may be called from probe context, we
* have to make sure that its lock, _stp_print_lock, can't
* possibly be held outside probe context too. We ensure this
* by grabbing the context here, so any probe triggered by this
* region will appear reentrant and be skipped rather than
* deadlock. Failure to get_context just means we're already
* in a probe, which is fine.
*
* (see also _stp_ctl_send for a similar situation)
*
* A better solution would be to replace this
* concurrency-control-laden effort with a lockless
* algorithm.
*/
c = _stp_runtime_entryfn_get_context();
dbug_trans(1, "calling _stp_data_write...\n");
stp_spin_lock_irqsave(&_stp_print_lock, flags);
while (len > 0) {
size_t bytes_reserved;
bytes_reserved = _stp_data_write_reserve(len, &entry);
if (likely(entry && bytes_reserved > 0)) {
memcpy(_stp_data_entry_data(entry), bufp,
bytes_reserved);
_stp_data_write_commit(entry);
bufp += bytes_reserved;
len -= bytes_reserved;
}
else {
atomic_inc(&_stp_transport_failures);
break;
}
}
stp_spin_unlock_irqrestore(&_stp_print_lock, flags);
_stp_runtime_entryfn_put_context(c);
}
#endif /* STP_TRANSPORT_VERSION != 1 */
#endif /* !STP_BULKMODE */
}
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