Re: [PATCH v3] qemu/atomic.h: rename atomic_ to qatomic_

[Matthew Rosato <mjrosato@xxxxxxxxxxxxx>]

On 9/23/20 6:56 AM, Stefan Hajnoczi wrote:
> 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@xxxxxxxxxx>
..snip..
> diff --git 
> a/include/standard-headers/drivers/infiniband/hw/vmw_pvrdma/pvrdma_ring.h 
> b/include/standard-headers/drivers/infiniband/hw/vmw_pvrdma/pvrdma_ring.h
> index acd4c8346d..7b4062a1a1 100644
> --- a/include/standard-headers/drivers/infiniband/hw/vmw_pvrdma/pvrdma_ring.h
> +++ b/include/standard-headers/drivers/infiniband/hw/vmw_pvrdma/pvrdma_ring.h
> @@ -68,7 +68,7 @@ static inline int pvrdma_idx_valid(uint32_t idx, uint32_t 
> max_elems)
>   
>   static inline int32_t pvrdma_idx(int *var, uint32_t max_elems)
>   {
> -       const unsigned int idx = atomic_read(var);
> +       const unsigned int idx = qatomic_read(var);
>   
>   	if (pvrdma_idx_valid(idx, max_elems))
>                 return idx & (max_elems - 1);
> @@ -77,17 +77,17 @@ static inline int32_t pvrdma_idx(int *var, uint32_t 
> max_elems)
>   
>   static inline void pvrdma_idx_ring_inc(int *var, uint32_t max_elems)
>   {
> -       uint32_t idx = atomic_read(var) + 1;    /* Increment. */
> +       uint32_t idx = qatomic_read(var) + 1;   /* Increment. */
>   
>   	idx &= (max_elems << 1) - 1;		/* Modulo size, flip gen. */
> -       atomic_set(var, idx);
> +       qatomic_set(var, idx);
>   }
>   
>   static inline int32_t pvrdma_idx_ring_has_space(const struct pvrdma_ring *r,
>                                               uint32_t max_elems, uint32_t 
> *out_tail)
>   {
> -       const uint32_t tail = atomic_read(&r->prod_tail);
> -       const uint32_t head = atomic_read(&r->cons_head);
> +       const uint32_t tail = qatomic_read(&r->prod_tail);
> +       const uint32_t head = qatomic_read(&r->cons_head);
>   
>   	if (pvrdma_idx_valid(tail, max_elems) &&
>             pvrdma_idx_valid(head, max_elems)) {
> @@ -100,8 +100,8 @@ static inline int32_t pvrdma_idx_ring_has_space(const 
> struct pvrdma_ring *r,
>   static inline int32_t pvrdma_idx_ring_has_data(const struct pvrdma_ring *r,
>                                              uint32_t max_elems, uint32_t 
> *out_head)
>   {
> -       const uint32_t tail = atomic_read(&r->prod_tail);
> -       const uint32_t head = atomic_read(&r->cons_head);
> +       const uint32_t tail = qatomic_read(&r->prod_tail);
> +       const uint32_t head = qatomic_read(&r->cons_head);
>   
>   	if (pvrdma_idx_valid(tail, max_elems) &&
>             pvrdma_idx_valid(head, max_elems)) {

It looks like the changes in this file are going to get reverted the 
next time someone does a linux header sync.