mirror of
https://github.com/xemu-project/xemu.git
synced 2024-11-23 03:29:43 +00:00
d73415a315
clang's C11 atomic_fetch_*() functions only take a C11 atomic type
pointer argument. QEMU uses direct types (int, etc) and this causes a
compiler error when a QEMU code calls these functions in a source file
that also included <stdatomic.h> via a system header file:
$ CC=clang CXX=clang++ ./configure ... && make
../util/async.c:79:17: error: address argument to atomic operation must be a pointer to _Atomic type ('unsigned int *' invalid)
Avoid using atomic_*() names in QEMU's atomic.h since that namespace is
used by <stdatomic.h>. Prefix QEMU's APIs with 'q' so that atomic.h
and <stdatomic.h> can co-exist. I checked /usr/include on my machine and
searched GitHub for existing "qatomic_" users but there seem to be none.
This patch was generated using:
$ git grep -h -o '\<atomic\(64\)\?_[a-z0-9_]\+' include/qemu/atomic.h | \
sort -u >/tmp/changed_identifiers
$ for identifier in $(</tmp/changed_identifiers); do
sed -i "s%\<$identifier\>%q$identifier%g" \
$(git grep -I -l "\<$identifier\>")
done
I manually fixed line-wrap issues and misaligned rST tables.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20200923105646.47864-1-stefanha@redhat.com>
138 lines
3.3 KiB
C
138 lines
3.3 KiB
C
/*
|
|
* Atomic operations on 64-bit quantities.
|
|
*
|
|
* Copyright (C) 2017 Red Hat, Inc.
|
|
*
|
|
* Author: Paolo Bonzini <pbonzini@redhat.com>
|
|
*
|
|
* This work is licensed under the terms of the GNU GPL, version 2 or later.
|
|
* See the COPYING file in the top-level directory.
|
|
*/
|
|
|
|
#include "qemu/osdep.h"
|
|
#include "qemu/atomic.h"
|
|
#include "qemu/stats64.h"
|
|
#include "qemu/processor.h"
|
|
|
|
#ifndef CONFIG_ATOMIC64
|
|
static inline void stat64_rdlock(Stat64 *s)
|
|
{
|
|
/* Keep out incoming writers to avoid them starving us. */
|
|
qatomic_add(&s->lock, 2);
|
|
|
|
/* If there is a concurrent writer, wait for it. */
|
|
while (qatomic_read(&s->lock) & 1) {
|
|
cpu_relax();
|
|
}
|
|
}
|
|
|
|
static inline void stat64_rdunlock(Stat64 *s)
|
|
{
|
|
qatomic_sub(&s->lock, 2);
|
|
}
|
|
|
|
static inline bool stat64_wrtrylock(Stat64 *s)
|
|
{
|
|
return qatomic_cmpxchg(&s->lock, 0, 1) == 0;
|
|
}
|
|
|
|
static inline void stat64_wrunlock(Stat64 *s)
|
|
{
|
|
qatomic_dec(&s->lock);
|
|
}
|
|
|
|
uint64_t stat64_get(const Stat64 *s)
|
|
{
|
|
uint32_t high, low;
|
|
|
|
stat64_rdlock((Stat64 *)s);
|
|
|
|
/* 64-bit writes always take the lock, so we can read in
|
|
* any order.
|
|
*/
|
|
high = qatomic_read(&s->high);
|
|
low = qatomic_read(&s->low);
|
|
stat64_rdunlock((Stat64 *)s);
|
|
|
|
return ((uint64_t)high << 32) | low;
|
|
}
|
|
|
|
bool stat64_add32_carry(Stat64 *s, uint32_t low, uint32_t high)
|
|
{
|
|
uint32_t old;
|
|
|
|
if (!stat64_wrtrylock(s)) {
|
|
cpu_relax();
|
|
return false;
|
|
}
|
|
|
|
/* 64-bit reads always take the lock, so they don't care about the
|
|
* order of our update. By updating s->low first, we can check
|
|
* whether we have to carry into s->high.
|
|
*/
|
|
old = qatomic_fetch_add(&s->low, low);
|
|
high += (old + low) < old;
|
|
qatomic_add(&s->high, high);
|
|
stat64_wrunlock(s);
|
|
return true;
|
|
}
|
|
|
|
bool stat64_min_slow(Stat64 *s, uint64_t value)
|
|
{
|
|
uint32_t high, low;
|
|
uint64_t orig;
|
|
|
|
if (!stat64_wrtrylock(s)) {
|
|
cpu_relax();
|
|
return false;
|
|
}
|
|
|
|
high = qatomic_read(&s->high);
|
|
low = qatomic_read(&s->low);
|
|
|
|
orig = ((uint64_t)high << 32) | low;
|
|
if (value < orig) {
|
|
/* We have to set low before high, just like stat64_min reads
|
|
* high before low. The value may become higher temporarily, but
|
|
* stat64_get does not notice (it takes the lock) and the only ill
|
|
* effect on stat64_min is that the slow path may be triggered
|
|
* unnecessarily.
|
|
*/
|
|
qatomic_set(&s->low, (uint32_t)value);
|
|
smp_wmb();
|
|
qatomic_set(&s->high, value >> 32);
|
|
}
|
|
stat64_wrunlock(s);
|
|
return true;
|
|
}
|
|
|
|
bool stat64_max_slow(Stat64 *s, uint64_t value)
|
|
{
|
|
uint32_t high, low;
|
|
uint64_t orig;
|
|
|
|
if (!stat64_wrtrylock(s)) {
|
|
cpu_relax();
|
|
return false;
|
|
}
|
|
|
|
high = qatomic_read(&s->high);
|
|
low = qatomic_read(&s->low);
|
|
|
|
orig = ((uint64_t)high << 32) | low;
|
|
if (value > orig) {
|
|
/* We have to set low before high, just like stat64_max reads
|
|
* high before low. The value may become lower temporarily, but
|
|
* stat64_get does not notice (it takes the lock) and the only ill
|
|
* effect on stat64_max is that the slow path may be triggered
|
|
* unnecessarily.
|
|
*/
|
|
qatomic_set(&s->low, (uint32_t)value);
|
|
smp_wmb();
|
|
qatomic_set(&s->high, value >> 32);
|
|
}
|
|
stat64_wrunlock(s);
|
|
return true;
|
|
}
|
|
#endif
|