/usr/share/systemtap/runtime/print_flush.c is in systemtap-common 2.6-0.2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 | /* -*- 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 DEFINE_SPINLOCK(_stp_print_lock);
void EXPORT_FN(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");
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;
}
}
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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