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Re: [Qemu-devel] [RFC PATCH] migration: do not use atomic__nocheck() fun
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [RFC PATCH] migration: do not use atomic__nocheck() functions directly |
Date: |
Fri, 19 Jan 2018 18:01:33 +0000 |
User-agent: |
Mutt/1.9.1 (2017-09-22) |
* Philippe Mathieu-Daudé (address@hidden) wrote:
> (incorrectly use in 3be98be4e9f)
>
> Signed-off-by: Philippe Mathieu-Daudé <address@hidden>
I'm a bit confused; isnt the only difference between the nocheck
versions that it'll fail at compile time instead of link?
Dave
> ---
> currently on ppc32 the linking fails:
>
> CC migration/postcopy-ram.o
> ...
> LINK microblaze-softmmu/qemu-system-microblaze
> ../migration/postcopy-ram.o: In function `mark_postcopy_blocktime_end':
> migration/postcopy-ram.c:717: undefined reference to `__atomic_fetch_add_8'
> migration/postcopy-ram.c:738: undefined reference to `__atomic_fetch_add_8'
> ../migration/postcopy-ram.o: In function `mark_postcopy_blocktime_begin':
> migration/postcopy-ram.c:651: undefined reference to `__atomic_exchange_8'
> migration/postcopy-ram.c:652: undefined reference to `__atomic_exchange_8'
> migration/postcopy-ram.c:661: undefined reference to `__atomic_exchange_8'
> collect2: error: ld returned 1 exit status
> Makefile:193: recipe for target 'qemu-system-microblaze' failed
> make[1]: *** [qemu-system-microblaze] Error 1
>
> with this patch the compilation fails:
>
> CC migration/postcopy-ram.o
> In file included from include/qemu/osdep.h:36:0,
> from migration/postcopy-ram.c:19:
> migration/postcopy-ram.c: In function 'mark_postcopy_blocktime_begin':
> include/qemu/compiler.h:86:30: error: static assertion failed: "not
> expecting: sizeof(*&dc->last_begin) > ATOMIC_REG_SIZE"
> #define QEMU_BUILD_BUG_ON(x) _Static_assert(!(x), "not expecting: " #x)
> ^
> include/qemu/atomic.h:183:5: note: in expansion of macro 'QEMU_BUILD_BUG_ON'
> QEMU_BUILD_BUG_ON(sizeof(*ptr) > ATOMIC_REG_SIZE); \
> ^
> migration/postcopy-ram.c:651:5: note: in expansion of macro 'atomic_xchg'
> atomic_xchg(&dc->last_begin, now_ms);
> ^
>
> migration/postcopy-ram.c | 12 ++++++------
> 1 file changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
> index 7814da5b4b..6ecc1aa820 100644
> --- a/migration/postcopy-ram.c
> +++ b/migration/postcopy-ram.c
> @@ -648,17 +648,17 @@ static void mark_postcopy_blocktime_begin(uintptr_t
> addr, uint32_t ptid,
> atomic_inc(&dc->smp_cpus_down);
> }
>
> - atomic_xchg__nocheck(&dc->last_begin, now_ms);
> - atomic_xchg__nocheck(&dc->page_fault_vcpu_time[cpu], now_ms);
> - atomic_xchg__nocheck(&dc->vcpu_addr[cpu], addr);
> + atomic_xchg(&dc->last_begin, now_ms);
> + atomic_xchg(&dc->page_fault_vcpu_time[cpu], now_ms);
> + atomic_xchg(&dc->vcpu_addr[cpu], addr);
>
> /* check it here, not at the begining of the function,
> * due to, check could accur early than bitmap_set in
> * qemu_ufd_copy_ioctl */
> already_received = ramblock_recv_bitmap_test(rb, (void *)addr);
> if (already_received) {
> - atomic_xchg__nocheck(&dc->vcpu_addr[cpu], 0);
> - atomic_xchg__nocheck(&dc->page_fault_vcpu_time[cpu], 0);
> + atomic_xchg(&dc->vcpu_addr[cpu], 0);
> + atomic_xchg(&dc->page_fault_vcpu_time[cpu], 0);
> atomic_dec(&dc->smp_cpus_down);
> }
> trace_mark_postcopy_blocktime_begin(addr, dc,
> dc->page_fault_vcpu_time[cpu],
> @@ -719,7 +719,7 @@ static void mark_postcopy_blocktime_end(uintptr_t addr)
> read_vcpu_time == 0) {
> continue;
> }
> - atomic_xchg__nocheck(&dc->vcpu_addr[i], 0);
> + atomic_xchg(&dc->vcpu_addr[i], 0);
> vcpu_blocktime = now_ms - read_vcpu_time;
> affected_cpu += 1;
> /* we need to know is that mark_postcopy_end was due to
> --
> 2.15.1
>
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK