mirror of
https://github.com/xemu-project/xemu.git
synced 2024-11-30 23:10:38 +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>
86 lines
2.0 KiB
C
86 lines
2.0 KiB
C
/*
|
|
* Seqlock implementation for QEMU
|
|
*
|
|
* Copyright Red Hat, Inc. 2013
|
|
*
|
|
* 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.
|
|
*
|
|
*/
|
|
|
|
#ifndef QEMU_SEQLOCK_H
|
|
#define QEMU_SEQLOCK_H
|
|
|
|
#include "qemu/atomic.h"
|
|
#include "qemu/thread.h"
|
|
#include "qemu/lockable.h"
|
|
|
|
typedef struct QemuSeqLock QemuSeqLock;
|
|
|
|
struct QemuSeqLock {
|
|
unsigned sequence;
|
|
};
|
|
|
|
static inline void seqlock_init(QemuSeqLock *sl)
|
|
{
|
|
sl->sequence = 0;
|
|
}
|
|
|
|
/* Lock out other writers and update the count. */
|
|
static inline void seqlock_write_begin(QemuSeqLock *sl)
|
|
{
|
|
qatomic_set(&sl->sequence, sl->sequence + 1);
|
|
|
|
/* Write sequence before updating other fields. */
|
|
smp_wmb();
|
|
}
|
|
|
|
static inline void seqlock_write_end(QemuSeqLock *sl)
|
|
{
|
|
/* Write other fields before finalizing sequence. */
|
|
smp_wmb();
|
|
|
|
qatomic_set(&sl->sequence, sl->sequence + 1);
|
|
}
|
|
|
|
/* Lock out other writers and update the count. */
|
|
static inline void seqlock_write_lock_impl(QemuSeqLock *sl, QemuLockable *lock)
|
|
{
|
|
qemu_lockable_lock(lock);
|
|
seqlock_write_begin(sl);
|
|
}
|
|
#define seqlock_write_lock(sl, lock) \
|
|
seqlock_write_lock_impl(sl, QEMU_MAKE_LOCKABLE(lock))
|
|
|
|
/* Update the count and release the lock. */
|
|
static inline void seqlock_write_unlock_impl(QemuSeqLock *sl, QemuLockable *lock)
|
|
{
|
|
seqlock_write_end(sl);
|
|
qemu_lockable_unlock(lock);
|
|
}
|
|
#define seqlock_write_unlock(sl, lock) \
|
|
seqlock_write_unlock_impl(sl, QEMU_MAKE_LOCKABLE(lock))
|
|
|
|
|
|
static inline unsigned seqlock_read_begin(const QemuSeqLock *sl)
|
|
{
|
|
/* Always fail if a write is in progress. */
|
|
unsigned ret = qatomic_read(&sl->sequence);
|
|
|
|
/* Read sequence before reading other fields. */
|
|
smp_rmb();
|
|
return ret & ~1;
|
|
}
|
|
|
|
static inline int seqlock_read_retry(const QemuSeqLock *sl, unsigned start)
|
|
{
|
|
/* Read other fields before reading final sequence. */
|
|
smp_rmb();
|
|
return unlikely(qatomic_read(&sl->sequence) != start);
|
|
}
|
|
|
|
#endif
|