The virtgpu driver prints the last_seq variable using the %ld or %lu format string, which does not work correctly on all architectures and causes this compiler warning on ARM:
drivers/gpu/drm/virtio/virtgpu_fence.c: In function 'virtio_timeline_value_str': drivers/gpu/drm/virtio/virtgpu_fence.c:64:22: warning: format '%lu' expects argument of type 'long unsigned int', but argument 4 has type 'long long int' [-Wformat=] snprintf(str, size, "%lu", atomic64_read(&fence->drv->last_seq)); ^ drivers/gpu/drm/virtio/virtgpu_debugfs.c: In function 'virtio_gpu_debugfs_irq_info': drivers/gpu/drm/virtio/virtgpu_debugfs.c:37:16: warning: format '%ld' expects argument of type 'long int', but argument 3 has type 'long long int' [-Wformat=] seq_printf(m, "fence %ld %lld\n", ^
In order to avoid the warnings, this changes the format strings to %llu and adds a cast to u64, which makes it work the same way everywhere.
Signed-off-by: Arnd Bergmann arnd@arndb.de
diff --git a/drivers/gpu/drm/virtio/virtgpu_debugfs.c b/drivers/gpu/drm/virtio/virtgpu_debugfs.c index db8b49101a8b..512263919282 100644 --- a/drivers/gpu/drm/virtio/virtgpu_debugfs.c +++ b/drivers/gpu/drm/virtio/virtgpu_debugfs.c @@ -34,8 +34,8 @@ virtio_gpu_debugfs_irq_info(struct seq_file *m, void *data) struct drm_info_node *node = (struct drm_info_node *) m->private; struct virtio_gpu_device *vgdev = node->minor->dev->dev_private;
- seq_printf(m, "fence %ld %lld\n", - atomic64_read(&vgdev->fence_drv.last_seq), + seq_printf(m, "fence %llu %lld\n", + (u64)atomic64_read(&vgdev->fence_drv.last_seq), vgdev->fence_drv.sync_seq); return 0; } diff --git a/drivers/gpu/drm/virtio/virtgpu_fence.c b/drivers/gpu/drm/virtio/virtgpu_fence.c index 1da632631dac..67097c9ce9c1 100644 --- a/drivers/gpu/drm/virtio/virtgpu_fence.c +++ b/drivers/gpu/drm/virtio/virtgpu_fence.c @@ -61,7 +61,7 @@ static void virtio_timeline_value_str(struct fence *f, char *str, int size) { struct virtio_gpu_fence *fence = to_virtio_fence(f);
- snprintf(str, size, "%lu", atomic64_read(&fence->drv->last_seq)); + snprintf(str, size, "%llu", (u64)atomic64_read(&fence->drv->last_seq)); }
static const struct fence_ops virtio_fence_ops = {
On Wed, Oct 07, 2015 at 12:41:21PM +0200, Arnd Bergmann wrote:
The virtgpu driver prints the last_seq variable using the %ld or %lu format string, which does not work correctly on all architectures and causes this compiler warning on ARM:
drivers/gpu/drm/virtio/virtgpu_fence.c: In function 'virtio_timeline_value_str': drivers/gpu/drm/virtio/virtgpu_fence.c:64:22: warning: format '%lu' expects argument of type 'long unsigned int', but argument 4 has type 'long long int' [-Wformat=] snprintf(str, size, "%lu", atomic64_read(&fence->drv->last_seq)); ^ drivers/gpu/drm/virtio/virtgpu_debugfs.c: In function 'virtio_gpu_debugfs_irq_info': drivers/gpu/drm/virtio/virtgpu_debugfs.c:37:16: warning: format '%ld' expects argument of type 'long int', but argument 3 has type 'long long int' [-Wformat=] seq_printf(m, "fence %ld %lld\n", ^
In order to avoid the warnings, this changes the format strings to %llu and adds a cast to u64, which makes it work the same way everywhere.
You have to wonder why atomic64_* functions do not use u64 types. If they're not reliant on manipulating 64-bit quantities, then what's the point of calling them atomic _64_.
On Wednesday 07 October 2015 11:45:02 Russell King - ARM Linux wrote:
On Wed, Oct 07, 2015 at 12:41:21PM +0200, Arnd Bergmann wrote:
The virtgpu driver prints the last_seq variable using the %ld or %lu format string, which does not work correctly on all architectures and causes this compiler warning on ARM:
drivers/gpu/drm/virtio/virtgpu_fence.c: In function 'virtio_timeline_value_str': drivers/gpu/drm/virtio/virtgpu_fence.c:64:22: warning: format '%lu' expects argument of type 'long unsigned int', but argument 4 has type 'long long int' [-Wformat=] snprintf(str, size, "%lu", atomic64_read(&fence->drv->last_seq)); ^ drivers/gpu/drm/virtio/virtgpu_debugfs.c: In function 'virtio_gpu_debugfs_irq_info': drivers/gpu/drm/virtio/virtgpu_debugfs.c:37:16: warning: format '%ld' expects argument of type 'long int', but argument 3 has type 'long long int' [-Wformat=] seq_printf(m, "fence %ld %lld\n", ^
In order to avoid the warnings, this changes the format strings to %llu and adds a cast to u64, which makes it work the same way everywhere.
You have to wonder why atomic64_* functions do not use u64 types. If they're not reliant on manipulating 64-bit quantities, then what's the point of calling them atomic _64_.
I haven't checked all architectures, but I assume what happens is that 64-bit ones just #define atomic64_t atomic_long_t, so they don't have to provide three sets of functions.
Arnd
On Wednesday 07 October 2015 13:04:06 Arnd Bergmann wrote:
On Wednesday 07 October 2015 11:45:02 Russell King - ARM Linux wrote:
On Wed, Oct 07, 2015 at 12:41:21PM +0200, Arnd Bergmann wrote:
The virtgpu driver prints the last_seq variable using the %ld or %lu format string, which does not work correctly on all architectures and causes this compiler warning on ARM:
drivers/gpu/drm/virtio/virtgpu_fence.c: In function 'virtio_timeline_value_str': drivers/gpu/drm/virtio/virtgpu_fence.c:64:22: warning: format '%lu' expects argument of type 'long unsigned int', but argument 4 has type 'long long int' [-Wformat=] snprintf(str, size, "%lu", atomic64_read(&fence->drv->last_seq)); ^ drivers/gpu/drm/virtio/virtgpu_debugfs.c: In function 'virtio_gpu_debugfs_irq_info': drivers/gpu/drm/virtio/virtgpu_debugfs.c:37:16: warning: format '%ld' expects argument of type 'long int', but argument 3 has type 'long long int' [-Wformat=] seq_printf(m, "fence %ld %lld\n", ^
In order to avoid the warnings, this changes the format strings to %llu and adds a cast to u64, which makes it work the same way everywhere.
You have to wonder why atomic64_* functions do not use u64 types. If they're not reliant on manipulating 64-bit quantities, then what's the point of calling them atomic _64_.
I haven't checked all architectures, but I assume what happens is that 64-bit ones just #define atomic64_t atomic_long_t, so they don't have to provide three sets of functions.
scratch that, I just looked at all the architectures and found that it's just completely arbitrary, even within one architecture you get a mix of 'long' and 'long long', plus this gem from MIPS:
static __inline__ int atomic64_add_unless(atomic64_t *v, long a, long u)
which truncates the result to 32 bit.
Arnd
On Wed, Oct 7, 2015 at 1:23 PM, Arnd Bergmann arnd@arndb.de wrote:
On Wednesday 07 October 2015 13:04:06 Arnd Bergmann wrote:
On Wednesday 07 October 2015 11:45:02 Russell King - ARM Linux wrote:
On Wed, Oct 07, 2015 at 12:41:21PM +0200, Arnd Bergmann wrote:
The virtgpu driver prints the last_seq variable using the %ld or %lu format string, which does not work correctly on all architectures and causes this compiler warning on ARM:
drivers/gpu/drm/virtio/virtgpu_fence.c: In function 'virtio_timeline_value_str': drivers/gpu/drm/virtio/virtgpu_fence.c:64:22: warning: format '%lu' expects argument of type 'long unsigned int', but argument 4 has type 'long long int' [-Wformat=] snprintf(str, size, "%lu", atomic64_read(&fence->drv->last_seq)); ^ drivers/gpu/drm/virtio/virtgpu_debugfs.c: In function 'virtio_gpu_debugfs_irq_info': drivers/gpu/drm/virtio/virtgpu_debugfs.c:37:16: warning: format '%ld' expects argument of type 'long int', but argument 3 has type 'long long int' [-Wformat=] seq_printf(m, "fence %ld %lld\n", ^
In order to avoid the warnings, this changes the format strings to %llu and adds a cast to u64, which makes it work the same way everywhere.
You have to wonder why atomic64_* functions do not use u64 types. If they're not reliant on manipulating 64-bit quantities, then what's the point of calling them atomic _64_.
I haven't checked all architectures, but I assume what happens is that 64-bit ones just #define atomic64_t atomic_long_t, so they don't have to provide three sets of functions.
scratch that, I just looked at all the architectures and found that it's just completely arbitrary, even within one architecture you get a mix of 'long' and 'long long', plus this gem from MIPS:
static __inline__ int atomic64_add_unless(atomic64_t *v, long a, long u)
which truncates the result to 32 bit.
Woops.
See also my unanswered question in "atomic64 on 32-bit vs 64-bit (was: Re: Add virtio gpu driver.)", which is still valid: https://lkml.org/lkml/2015/6/28/18
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
On Monday 19 October 2015 09:34:15 Geert Uytterhoeven wrote:
On Wed, Oct 7, 2015 at 1:23 PM, Arnd Bergmann arnd@arndb.de wrote:
static __inline__ int atomic64_add_unless(atomic64_t *v, long a, long u)
which truncates the result to 32 bit.
Woops.
See also my unanswered question in "atomic64 on 32-bit vs 64-bit (was: Re: Add virtio gpu driver.)", which is still valid: https://lkml.org/lkml/2015/6/28/18
Regarding your question of
Instead of sprinkling casts, is there any good reason why atomic64_read() and atomic64_t aren't "long long" everywhere, cfr. u64?
I assume the answer is that some (all?) 64-bit architectures intentionally return 'long' here, in order for atomic_long_read() to return 'long' on all architectures, given the definitions from include/asm-generic/atomic-long.h
We would have to either change those, or we have to pick between atomic_long_* or atomic64_* to have a consistent return type.
Arnd
On Mon, Oct 19, 2015 at 12:11 PM, Arnd Bergmann arnd@arndb.de wrote:
On Monday 19 October 2015 09:34:15 Geert Uytterhoeven wrote:
On Wed, Oct 7, 2015 at 1:23 PM, Arnd Bergmann arnd@arndb.de wrote:
static __inline__ int atomic64_add_unless(atomic64_t *v, long a, long u)
which truncates the result to 32 bit.
Woops.
See also my unanswered question in "atomic64 on 32-bit vs 64-bit (was: Re: Add virtio gpu driver.)", which is still valid: https://lkml.org/lkml/2015/6/28/18
Regarding your question of
Instead of sprinkling casts, is there any good reason why atomic64_read() and atomic64_t aren't "long long" everywhere, cfr. u64?
I assume the answer is that some (all?) 64-bit architectures intentionally return 'long' here, in order for atomic_long_read() to return 'long' on all architectures, given the definitions from include/asm-generic/atomic-long.h
We would have to either change those, or we have to pick between atomic_long_* or atomic64_* to have a consistent return type.
I guess the main reason is this comment in include/asm-generic/atomic-long.h, which I hadn't noticed before:
* Casts for parameters are avoided for existing atomic functions in order to * avoid issues with cast-as-lval under gcc 4.x and other limitations that the * macros of a platform may have.
Still, it's a pity, as printing atomic_64 is one more place where casts are needed in callers.
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
On Wed, Oct 07, 2015 at 01:23:07PM +0200, Arnd Bergmann wrote:
I haven't checked all architectures, but I assume what happens is that 64-bit ones just #define atomic64_t atomic_long_t, so they don't have to provide three sets of functions.
scratch that, I just looked at all the architectures and found that it's just completely arbitrary, even within one architecture you get a mix of 'long' and 'long long', plus this gem from MIPS:
static __inline__ int atomic64_add_unless(atomic64_t *v, long a, long u)
which truncates the result to 32 bit.
Eh... The result is 0/1 so nothing is truncated. Alpha, MIPS, PARISC and PowerPC are using the same prototype and x86 only differs in the use of inline instead __inline__. And anyway, that function on MIPS is only built for CONFIG_64BIT.
What's wrong on MIPS is the comment describing the function's return value which was changed by f24219b4e90cf70ec4a211b17fbabc725a0ddf3c (atomic: move atomic_add_unless to generic code) and I've queued up a patch to fix that since a few days. I guess that was a cut and paste error from __atomic_add_unless which indeed does return the old value.
Ralf
On Monday 19 October 2015 11:37:00 Ralf Baechle wrote:
On Wed, Oct 07, 2015 at 01:23:07PM +0200, Arnd Bergmann wrote:
I haven't checked all architectures, but I assume what happens is that 64-bit ones just #define atomic64_t atomic_long_t, so they don't have to provide three sets of functions.
scratch that, I just looked at all the architectures and found that it's just completely arbitrary, even within one architecture you get a mix of 'long' and 'long long', plus this gem from MIPS:
static __inline__ int atomic64_add_unless(atomic64_t *v, long a, long u)
which truncates the result to 32 bit.
Eh... The result is 0/1 so nothing is truncated. Alpha, MIPS, PARISC and PowerPC are using the same prototype and x86 only differs in the use of inline instead __inline__. And anyway, that function on MIPS is only built for CONFIG_64BIT.
Ah, got it. Sorry about that.
What's wrong on MIPS is the comment describing the function's return value which was changed by f24219b4e90cf70ec4a211b17fbabc725a0ddf3c (atomic: move atomic_add_unless to generic code) and I've queued up a patch to fix that since a few days. I guess that was a cut and paste error from __atomic_add_unless which indeed does return the old value.
Thanks!
Arnd
dri-devel@lists.freedesktop.org
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Arnd Bergmann -
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Ralf Baechle -
Russell King - ARM Linux