qemu/atomic.h: rename atomic_ to qatomic_

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>

linux-user/hppa/cpu_loop.c

@@ -39,7 +39,7 @@ static abi_ulong hppa_lws(CPUHPPAState *env)
         }
         old = tswap32(old);
         new = tswap32(new);
-        ret = atomic_cmpxchg((uint32_t *)g2h(addr), old, new);
+        ret = qatomic_cmpxchg((uint32_t *)g2h(addr), old, new);
         ret = tswap32(ret);
         break;
 
@@ -60,19 +60,19 @@ static abi_ulong hppa_lws(CPUHPPAState *env)
         case 0:
             old = *(uint8_t *)g2h(old);
             new = *(uint8_t *)g2h(new);
-            ret = atomic_cmpxchg((uint8_t *)g2h(addr), old, new);
+            ret = qatomic_cmpxchg((uint8_t *)g2h(addr), old, new);
             ret = ret != old;
             break;
         case 1:
             old = *(uint16_t *)g2h(old);
             new = *(uint16_t *)g2h(new);
-            ret = atomic_cmpxchg((uint16_t *)g2h(addr), old, new);
+            ret = qatomic_cmpxchg((uint16_t *)g2h(addr), old, new);
             ret = ret != old;
             break;
         case 2:
             old = *(uint32_t *)g2h(old);
             new = *(uint32_t *)g2h(new);
-            ret = atomic_cmpxchg((uint32_t *)g2h(addr), old, new);
+            ret = qatomic_cmpxchg((uint32_t *)g2h(addr), old, new);
             ret = ret != old;
             break;
         case 3:
@@ -81,7 +81,8 @@ static abi_ulong hppa_lws(CPUHPPAState *env)
                 o64 = *(uint64_t *)g2h(old);
                 n64 = *(uint64_t *)g2h(new);
 #ifdef CONFIG_ATOMIC64
-                r64 = atomic_cmpxchg__nocheck((uint64_t *)g2h(addr), o64, n64);
+                r64 = qatomic_cmpxchg__nocheck((uint64_t *)g2h(addr),
+                                               o64, n64);
                 ret = r64 != o64;
 #else
                 start_exclusive();

linux-user/qemu.h

@@ -146,7 +146,7 @@ typedef struct TaskState {
     /* Nonzero if process_pending_signals() needs to do something (either
      * handle a pending signal or unblock signals).
      * This flag is written from a signal handler so should be accessed via
-     * the atomic_read() and atomic_set() functions. (It is not accessed
+     * the qatomic_read() and qatomic_set() functions. (It is not accessed
      * from multiple threads.)
      */
     int signal_pending;

linux-user/signal.c

@@ -195,7 +195,7 @@ int block_signals(void)
     sigfillset(&set);
     sigprocmask(SIG_SETMASK, &set, 0);
 
-    return atomic_xchg(&ts->signal_pending, 1);
+    return qatomic_xchg(&ts->signal_pending, 1);
 }
 
 /* Wrapper for sigprocmask function
@@ -688,7 +688,7 @@ int queue_signal(CPUArchState *env, int sig, int si_type,
     ts->sync_signal.info = *info;
     ts->sync_signal.pending = sig;
     /* signal that a new signal is pending */
-    atomic_set(&ts->signal_pending, 1);
+    qatomic_set(&ts->signal_pending, 1);
     return 1; /* indicates that the signal was queued */
 }
 
@@ -1005,7 +1005,7 @@ void process_pending_signals(CPUArchState *cpu_env)
     sigset_t set;
     sigset_t *blocked_set;
 
-    while (atomic_read(&ts->signal_pending)) {
+    while (qatomic_read(&ts->signal_pending)) {
         /* FIXME: This is not threadsafe.  */
         sigfillset(&set);
         sigprocmask(SIG_SETMASK, &set, 0);
@@ -1049,7 +1049,7 @@ void process_pending_signals(CPUArchState *cpu_env)
          * of unblocking might cause us to take another host signal which
          * will set signal_pending again).
          */
-        atomic_set(&ts->signal_pending, 0);
+        qatomic_set(&ts->signal_pending, 0);
         ts->in_sigsuspend = 0;
         set = ts->signal_mask;
         sigdelset(&set, SIGSEGV);