Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Wed, Nov 11, 2015 at 03:40:15PM -0800, Alexei Starovoitov wrote: > On Wed, Nov 11, 2015 at 11:21:35PM +0100, Peter Zijlstra wrote: > > On Wed, Nov 11, 2015 at 11:55:59AM -0800, Alexei Starovoitov wrote: > > > Therefore things like memory barriers, full set of atomics are not > > > applicable >

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Wed, Nov 11, 2015 at 03:40:15PM -0800, Alexei Starovoitov wrote: > On Wed, Nov 11, 2015 at 11:21:35PM +0100, Peter Zijlstra wrote: > > On Wed, Nov 11, 2015 at 11:55:59AM -0800, Alexei Starovoitov wrote: > > > Therefore things like memory barriers, full set of atomics are not > > > applicable >

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Wed, Nov 11, 2015 at 11:21:35PM +0100, Peter Zijlstra wrote: > On Wed, Nov 11, 2015 at 11:55:59AM -0800, Alexei Starovoitov wrote: > > Therefore things like memory barriers, full set of atomics are not > > applicable > > in bpf world. > > There are still plenty of wait-free constructs one can

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Wed, Nov 11, 2015 at 11:55:59AM -0800, Alexei Starovoitov wrote: > Therefore things like memory barriers, full set of atomics are not applicable > in bpf world. There are still plenty of wait-free constructs one can make using them. Say a barrier/rendezvous construct for knowing when an event

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Wed, Nov 11, 2015 at 07:54:15PM +0100, Peter Zijlstra wrote: > On Wed, Nov 11, 2015 at 07:44:27PM +0100, Peter Zijlstra wrote: > > On Wed, Nov 11, 2015 at 07:31:28PM +0100, Peter Zijlstra wrote: > > > > Add new one that does 'fetch_and_add' ? What is the real use case it > > > > will be used

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On 11/11/2015 08:23 PM, Peter Zijlstra wrote: On Wed, Nov 11, 2015 at 07:50:15PM +0100, Daniel Borkmann wrote: Well, on that note, it's not like you just change the target to bpf in your Makefile and can compile (& load into the kernel) anything you want with it. You do have to write small,

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Wed, Nov 11, 2015 at 07:50:15PM +0100, Daniel Borkmann wrote: > Well, on that note, it's not like you just change the target to bpf in your > Makefile and can compile (& load into the kernel) anything you want with it. > You do have to write small, restricted programs from scratch for a

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

From: Daniel Borkmann Date: Wed, 11 Nov 2015 19:50:15 +0100 > Well, on that note, it's not like you just change the target to bpf > in your Makefile and can compile (& load into the kernel) anything > you want with it. You do have to write small, restricted programs > from scratch for a

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

From: Alexei Starovoitov Date: Wed, 11 Nov 2015 10:11:33 -0800 > bpf_xadd was never meant to be __sync_fetch_and_add equivalent. > From the day one it meant to be atomic_add() as kernel does it. +1 > I did piggy back on __sync in the llvm backend because it was the quick > and dirty way to

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

From: Will Deacon Date: Wed, 11 Nov 2015 17:44:01 + > On Wed, Nov 11, 2015 at 12:35:48PM -0500, David Miller wrote: >> From: Alexei Starovoitov >> Date: Wed, 11 Nov 2015 09:27:00 -0800 >> >> > BPF_XADD == atomic_add() in kernel. period. >> > we are not going to deprecate it or introduce

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Wed, Nov 11, 2015 at 07:44:27PM +0100, Peter Zijlstra wrote: > On Wed, Nov 11, 2015 at 07:31:28PM +0100, Peter Zijlstra wrote: > > > Add new one that does 'fetch_and_add' ? What is the real use case it > > > will be used for? > > > > Look at all the atomic_{add,dec}_return*() users in the

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On 11/11/2015 07:31 PM, Peter Zijlstra wrote: On Wed, Nov 11, 2015 at 10:11:33AM -0800, Alexei Starovoitov wrote: On Wed, Nov 11, 2015 at 06:57:41PM +0100, Peter Zijlstra wrote: On Wed, Nov 11, 2015 at 12:35:48PM -0500, David Miller wrote: From: Alexei Starovoitov Date: Wed, 11 Nov 2015

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Wed, Nov 11, 2015 at 10:11:33AM -0800, Alexei Starovoitov wrote: > On Wed, Nov 11, 2015 at 06:57:41PM +0100, Peter Zijlstra wrote: > > On Wed, Nov 11, 2015 at 12:35:48PM -0500, David Miller wrote: > > > From: Alexei Starovoitov > > > Date: Wed, 11 Nov 2015 09:27:00 -0800 > > > > > > >

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Wed, Nov 11, 2015 at 07:31:28PM +0100, Peter Zijlstra wrote: > > Add new one that does 'fetch_and_add' ? What is the real use case it > > will be used for? > > Look at all the atomic_{add,dec}_return*() users in the kernel. A typical > example would be a reader-writer lock implementations. See

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Wed, Nov 11, 2015 at 07:31:28PM +0100, Peter Zijlstra wrote: > > Adding new intrinsic to llvm is not a big deal. I'll add it as soon > > as I have time to work on it or if somebody beats me to it I would be > > glad to test it and apply it. > > This isn't a speed coding contest. You want to

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Wed, Nov 11, 2015 at 10:11:33AM -0800, Alexei Starovoitov wrote: > On Wed, Nov 11, 2015 at 06:57:41PM +0100, Peter Zijlstra wrote: > > On Wed, Nov 11, 2015 at 12:35:48PM -0500, David Miller wrote: > > > From: Alexei Starovoitov > > > Date: Wed, 11 Nov 2015 09:27:00 -0800 > > > > > > >

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Wed, Nov 11, 2015 at 06:57:41PM +0100, Peter Zijlstra wrote: > On Wed, Nov 11, 2015 at 12:35:48PM -0500, David Miller wrote: > > From: Alexei Starovoitov > > Date: Wed, 11 Nov 2015 09:27:00 -0800 > > > > > BPF_XADD == atomic_add() in kernel. period. > > > we are not going to deprecate it or

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Wed, Nov 11, 2015 at 12:35:48PM -0500, David Miller wrote: > From: Alexei Starovoitov > Date: Wed, 11 Nov 2015 09:27:00 -0800 > > > BPF_XADD == atomic_add() in kernel. period. > > we are not going to deprecate it or introduce something else. > > Agreed, it makes no sense to try and tie C99

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Wed, Nov 11, 2015 at 12:35:48PM -0500, David Miller wrote: > From: Alexei Starovoitov > Date: Wed, 11 Nov 2015 09:27:00 -0800 > > > BPF_XADD == atomic_add() in kernel. period. > > we are not going to deprecate it or introduce something else. > > Agreed, it makes no sense to try and tie C99

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

From: Alexei Starovoitov Date: Wed, 11 Nov 2015 09:27:00 -0800 > BPF_XADD == atomic_add() in kernel. period. > we are not going to deprecate it or introduce something else. Agreed, it makes no sense to try and tie C99 or whatever atomic semantics to something that is already clearly defined to

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Wed, Nov 11, 2015 at 04:23:41PM +, Will Deacon wrote: > > If we're going to document it, a bug tracker might be a good place to > start. The behaviour, as it stands, is broken wrt the definition of the > __sync primitives. That is, there is no way to build __sync_fetch_and_add > out of

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

Hi Daniel, Thanks for investigating this further. On Wed, Nov 11, 2015 at 04:52:00PM +0100, Daniel Borkmann wrote: > I played a bit around with eBPF code to assign the __sync_fetch_and_add() > return value to a var and dump it to trace pipe, or use it as return code. > llvm compiles it (with the

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On 11/11/2015 01:58 PM, Peter Zijlstra wrote: On Wed, Nov 11, 2015 at 12:38:31PM +, Will Deacon wrote: Hmm, gcc doesn't have an eBPF compiler backend, so this won't work on gcc at all. The eBPF backend in LLVM recognizes the __sync_fetch_and_add() keyword and maps that to a BPF_XADD version

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Wed, Nov 11, 2015 at 12:38:31PM +, Will Deacon wrote: > > Hmm, gcc doesn't have an eBPF compiler backend, so this won't work on > > gcc at all. The eBPF backend in LLVM recognizes the __sync_fetch_and_add() > > keyword and maps that to a BPF_XADD version (BPF_W or BPF_DW). In the > >

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Wed, Nov 11, 2015 at 01:21:04PM +0100, Daniel Borkmann wrote: > On 11/11/2015 12:58 PM, Will Deacon wrote: > >On Wed, Nov 11, 2015 at 11:42:11AM +0100, Daniel Borkmann wrote: > >>On 11/11/2015 11:24 AM, Will Deacon wrote: > >>>On Wed, Nov 11, 2015 at 09:49:48AM +0100, Arnd Bergmann wrote: >

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On 11/11/2015 12:58 PM, Will Deacon wrote: On Wed, Nov 11, 2015 at 11:42:11AM +0100, Daniel Borkmann wrote: On 11/11/2015 11:24 AM, Will Deacon wrote: On Wed, Nov 11, 2015 at 09:49:48AM +0100, Arnd Bergmann wrote: On Tuesday 10 November 2015 18:52:45 Z Lim wrote: On Tue, Nov 10, 2015 at 4:42

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

Hi Daniel, On Wed, Nov 11, 2015 at 11:42:11AM +0100, Daniel Borkmann wrote: > On 11/11/2015 11:24 AM, Will Deacon wrote: > >On Wed, Nov 11, 2015 at 09:49:48AM +0100, Arnd Bergmann wrote: > >>On Tuesday 10 November 2015 18:52:45 Z Lim wrote: > >>>On Tue, Nov 10, 2015 at 4:42 PM, Alexei Starovoitov

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On 11/11/2015 11:24 AM, Will Deacon wrote: On Wed, Nov 11, 2015 at 09:49:48AM +0100, Arnd Bergmann wrote: On Tuesday 10 November 2015 18:52:45 Z Lim wrote: On Tue, Nov 10, 2015 at 4:42 PM, Alexei Starovoitov wrote: On Tue, Nov 10, 2015 at 04:26:02PM -0800, Shi, Yang wrote: On 11/10/2015

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Wed, Nov 11, 2015 at 09:49:48AM +0100, Arnd Bergmann wrote: > On Tuesday 10 November 2015 18:52:45 Z Lim wrote: > > On Tue, Nov 10, 2015 at 4:42 PM, Alexei Starovoitov > > wrote: > > > On Tue, Nov 10, 2015 at 04:26:02PM -0800, Shi, Yang wrote: > > >> On 11/10/2015 4:08 PM, Eric Dumazet wrote:

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Tuesday 10 November 2015 18:52:45 Z Lim wrote: > On Tue, Nov 10, 2015 at 4:42 PM, Alexei Starovoitov > wrote: > > On Tue, Nov 10, 2015 at 04:26:02PM -0800, Shi, Yang wrote: > >> On 11/10/2015 4:08 PM, Eric Dumazet wrote: > >> >On Tue, 2015-11-10 at 14:41 -0800, Yang Shi wrote: > >> >>aarch64

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Tuesday 10 November 2015 18:52:45 Z Lim wrote: > On Tue, Nov 10, 2015 at 4:42 PM, Alexei Starovoitov > wrote: > > On Tue, Nov 10, 2015 at 04:26:02PM -0800, Shi, Yang wrote: > >> On 11/10/2015 4:08 PM, Eric Dumazet wrote: > >> >On Tue, 2015-11-10 at 14:41 -0800,

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On 11/11/2015 11:24 AM, Will Deacon wrote: On Wed, Nov 11, 2015 at 09:49:48AM +0100, Arnd Bergmann wrote: On Tuesday 10 November 2015 18:52:45 Z Lim wrote: On Tue, Nov 10, 2015 at 4:42 PM, Alexei Starovoitov wrote: On Tue, Nov 10, 2015 at 04:26:02PM -0800, Shi,

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Wed, Nov 11, 2015 at 09:49:48AM +0100, Arnd Bergmann wrote: > On Tuesday 10 November 2015 18:52:45 Z Lim wrote: > > On Tue, Nov 10, 2015 at 4:42 PM, Alexei Starovoitov > > wrote: > > > On Tue, Nov 10, 2015 at 04:26:02PM -0800, Shi, Yang wrote: > > >> On 11/10/2015

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Wed, Nov 11, 2015 at 12:38:31PM +, Will Deacon wrote: > > Hmm, gcc doesn't have an eBPF compiler backend, so this won't work on > > gcc at all. The eBPF backend in LLVM recognizes the __sync_fetch_and_add() > > keyword and maps that to a BPF_XADD version (BPF_W or BPF_DW). In the > >

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Wed, Nov 11, 2015 at 12:35:48PM -0500, David Miller wrote: > From: Alexei Starovoitov > Date: Wed, 11 Nov 2015 09:27:00 -0800 > > > BPF_XADD == atomic_add() in kernel. period. > > we are not going to deprecate it or introduce something else. > > Agreed, it makes

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Wed, Nov 11, 2015 at 04:23:41PM +, Will Deacon wrote: > > If we're going to document it, a bug tracker might be a good place to > start. The behaviour, as it stands, is broken wrt the definition of the > __sync primitives. That is, there is no way to build __sync_fetch_and_add > out of

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Wed, Nov 11, 2015 at 12:35:48PM -0500, David Miller wrote: > From: Alexei Starovoitov > Date: Wed, 11 Nov 2015 09:27:00 -0800 > > > BPF_XADD == atomic_add() in kernel. period. > > we are not going to deprecate it or introduce something else. > > Agreed, it makes

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Wed, Nov 11, 2015 at 06:57:41PM +0100, Peter Zijlstra wrote: > On Wed, Nov 11, 2015 at 12:35:48PM -0500, David Miller wrote: > > From: Alexei Starovoitov > > Date: Wed, 11 Nov 2015 09:27:00 -0800 > > > > > BPF_XADD == atomic_add() in kernel. period. > > > we are

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

From: Alexei Starovoitov Date: Wed, 11 Nov 2015 09:27:00 -0800 > BPF_XADD == atomic_add() in kernel. period. > we are not going to deprecate it or introduce something else. Agreed, it makes no sense to try and tie C99 or whatever atomic semantics to something that

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On 11/11/2015 01:58 PM, Peter Zijlstra wrote: On Wed, Nov 11, 2015 at 12:38:31PM +, Will Deacon wrote: Hmm, gcc doesn't have an eBPF compiler backend, so this won't work on gcc at all. The eBPF backend in LLVM recognizes the __sync_fetch_and_add() keyword and maps that to a BPF_XADD version

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Wed, Nov 11, 2015 at 01:21:04PM +0100, Daniel Borkmann wrote: > On 11/11/2015 12:58 PM, Will Deacon wrote: > >On Wed, Nov 11, 2015 at 11:42:11AM +0100, Daniel Borkmann wrote: > >>On 11/11/2015 11:24 AM, Will Deacon wrote: > >>>On Wed, Nov 11, 2015 at 09:49:48AM +0100, Arnd Bergmann wrote: >

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

Hi Daniel, Thanks for investigating this further. On Wed, Nov 11, 2015 at 04:52:00PM +0100, Daniel Borkmann wrote: > I played a bit around with eBPF code to assign the __sync_fetch_and_add() > return value to a var and dump it to trace pipe, or use it as return code. > llvm compiles it (with the

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On 11/11/2015 12:58 PM, Will Deacon wrote: On Wed, Nov 11, 2015 at 11:42:11AM +0100, Daniel Borkmann wrote: On 11/11/2015 11:24 AM, Will Deacon wrote: On Wed, Nov 11, 2015 at 09:49:48AM +0100, Arnd Bergmann wrote: On Tuesday 10 November 2015 18:52:45 Z Lim wrote: On Tue, Nov 10, 2015 at 4:42

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

Hi Daniel, On Wed, Nov 11, 2015 at 11:42:11AM +0100, Daniel Borkmann wrote: > On 11/11/2015 11:24 AM, Will Deacon wrote: > >On Wed, Nov 11, 2015 at 09:49:48AM +0100, Arnd Bergmann wrote: > >>On Tuesday 10 November 2015 18:52:45 Z Lim wrote: > >>>On Tue, Nov 10, 2015 at 4:42 PM, Alexei Starovoitov

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Wed, Nov 11, 2015 at 11:21:35PM +0100, Peter Zijlstra wrote: > On Wed, Nov 11, 2015 at 11:55:59AM -0800, Alexei Starovoitov wrote: > > Therefore things like memory barriers, full set of atomics are not > > applicable > > in bpf world. > > There are still plenty of wait-free constructs one can

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Wed, Nov 11, 2015 at 07:31:28PM +0100, Peter Zijlstra wrote: > > Adding new intrinsic to llvm is not a big deal. I'll add it as soon > > as I have time to work on it or if somebody beats me to it I would be > > glad to test it and apply it. > > This isn't a speed coding contest. You want to

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Wed, Nov 11, 2015 at 10:11:33AM -0800, Alexei Starovoitov wrote: > On Wed, Nov 11, 2015 at 06:57:41PM +0100, Peter Zijlstra wrote: > > On Wed, Nov 11, 2015 at 12:35:48PM -0500, David Miller wrote: > > > From: Alexei Starovoitov > > > Date: Wed, 11 Nov 2015

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

From: Daniel Borkmann Date: Wed, 11 Nov 2015 19:50:15 +0100 > Well, on that note, it's not like you just change the target to bpf > in your Makefile and can compile (& load into the kernel) anything > you want with it. You do have to write small, restricted programs > from

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Wed, Nov 11, 2015 at 07:31:28PM +0100, Peter Zijlstra wrote: > > Add new one that does 'fetch_and_add' ? What is the real use case it > > will be used for? > > Look at all the atomic_{add,dec}_return*() users in the kernel. A typical > example would be a reader-writer lock implementations. See

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On 11/11/2015 07:31 PM, Peter Zijlstra wrote: On Wed, Nov 11, 2015 at 10:11:33AM -0800, Alexei Starovoitov wrote: On Wed, Nov 11, 2015 at 06:57:41PM +0100, Peter Zijlstra wrote: On Wed, Nov 11, 2015 at 12:35:48PM -0500, David Miller wrote: From: Alexei Starovoitov

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Wed, Nov 11, 2015 at 07:50:15PM +0100, Daniel Borkmann wrote: > Well, on that note, it's not like you just change the target to bpf in your > Makefile and can compile (& load into the kernel) anything you want with it. > You do have to write small, restricted programs from scratch for a

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On 11/11/2015 08:23 PM, Peter Zijlstra wrote: On Wed, Nov 11, 2015 at 07:50:15PM +0100, Daniel Borkmann wrote: Well, on that note, it's not like you just change the target to bpf in your Makefile and can compile (& load into the kernel) anything you want with it. You do have to write small,

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Wed, Nov 11, 2015 at 10:11:33AM -0800, Alexei Starovoitov wrote: > On Wed, Nov 11, 2015 at 06:57:41PM +0100, Peter Zijlstra wrote: > > On Wed, Nov 11, 2015 at 12:35:48PM -0500, David Miller wrote: > > > From: Alexei Starovoitov > > > Date: Wed, 11 Nov 2015

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

From: Alexei Starovoitov Date: Wed, 11 Nov 2015 10:11:33 -0800 > bpf_xadd was never meant to be __sync_fetch_and_add equivalent. > From the day one it meant to be atomic_add() as kernel does it. +1 > I did piggy back on __sync in the llvm backend because it was

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Wed, Nov 11, 2015 at 07:54:15PM +0100, Peter Zijlstra wrote: > On Wed, Nov 11, 2015 at 07:44:27PM +0100, Peter Zijlstra wrote: > > On Wed, Nov 11, 2015 at 07:31:28PM +0100, Peter Zijlstra wrote: > > > > Add new one that does 'fetch_and_add' ? What is the real use case it > > > > will be used

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Wed, Nov 11, 2015 at 07:44:27PM +0100, Peter Zijlstra wrote: > On Wed, Nov 11, 2015 at 07:31:28PM +0100, Peter Zijlstra wrote: > > > Add new one that does 'fetch_and_add' ? What is the real use case it > > > will be used for? > > > > Look at all the atomic_{add,dec}_return*() users in the

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

From: Will Deacon Date: Wed, 11 Nov 2015 17:44:01 + > On Wed, Nov 11, 2015 at 12:35:48PM -0500, David Miller wrote: >> From: Alexei Starovoitov >> Date: Wed, 11 Nov 2015 09:27:00 -0800 >> >> > BPF_XADD == atomic_add() in kernel. period. >>

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Wed, Nov 11, 2015 at 11:55:59AM -0800, Alexei Starovoitov wrote: > Therefore things like memory barriers, full set of atomics are not applicable > in bpf world. There are still plenty of wait-free constructs one can make using them. Say a barrier/rendezvous construct for knowing when an event

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

Yang, On Tue, Nov 10, 2015 at 4:42 PM, Alexei Starovoitov wrote: > On Tue, Nov 10, 2015 at 04:26:02PM -0800, Shi, Yang wrote: >> On 11/10/2015 4:08 PM, Eric Dumazet wrote: >> >On Tue, 2015-11-10 at 14:41 -0800, Yang Shi wrote: >> >>aarch64 doesn't have native support for XADD instruction,

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Tue, Nov 10, 2015 at 04:26:02PM -0800, Shi, Yang wrote: > On 11/10/2015 4:08 PM, Eric Dumazet wrote: > >On Tue, 2015-11-10 at 14:41 -0800, Yang Shi wrote: > >>aarch64 doesn't have native support for XADD instruction, implement it by > >>the below instruction sequence: > >> > >>Load (dst + off)

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On 11/10/2015 4:08 PM, Eric Dumazet wrote: On Tue, 2015-11-10 at 14:41 -0800, Yang Shi wrote: aarch64 doesn't have native support for XADD instruction, implement it by the below instruction sequence: Load (dst + off) to a register Add src to it Store it back to (dst + off) Not really what is

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Tue, 2015-11-10 at 14:41 -0800, Yang Shi wrote: > aarch64 doesn't have native support for XADD instruction, implement it by > the below instruction sequence: > > Load (dst + off) to a register > Add src to it > Store it back to (dst + off) Not really what is needed ? See this BPF_XADD as an

[PATCH 2/2] arm64: bpf: add BPF XADD instruction

aarch64 doesn't have native support for XADD instruction, implement it by the below instruction sequence: Load (dst + off) to a register Add src to it Store it back to (dst + off) Signed-off-by: Yang Shi CC: Zi Shen Lim CC: Xi Wang --- arch/arm64/net/bpf_jit_comp.c | 19 +++

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On 11/10/2015 4:08 PM, Eric Dumazet wrote: On Tue, 2015-11-10 at 14:41 -0800, Yang Shi wrote: aarch64 doesn't have native support for XADD instruction, implement it by the below instruction sequence: Load (dst + off) to a register Add src to it Store it back to (dst + off) Not really what is

[PATCH 2/2] arm64: bpf: add BPF XADD instruction

aarch64 doesn't have native support for XADD instruction, implement it by the below instruction sequence: Load (dst + off) to a register Add src to it Store it back to (dst + off) Signed-off-by: Yang Shi CC: Zi Shen Lim CC: Xi Wang

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Tue, 2015-11-10 at 14:41 -0800, Yang Shi wrote: > aarch64 doesn't have native support for XADD instruction, implement it by > the below instruction sequence: > > Load (dst + off) to a register > Add src to it > Store it back to (dst + off) Not really what is needed ? See this BPF_XADD as an

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

Yang, On Tue, Nov 10, 2015 at 4:42 PM, Alexei Starovoitov wrote: > On Tue, Nov 10, 2015 at 04:26:02PM -0800, Shi, Yang wrote: >> On 11/10/2015 4:08 PM, Eric Dumazet wrote: >> >On Tue, 2015-11-10 at 14:41 -0800, Yang Shi wrote: >> >>aarch64 doesn't have native

Re: [PATCH 2/2] arm64: bpf: add BPF XADD instruction

On Tue, Nov 10, 2015 at 04:26:02PM -0800, Shi, Yang wrote: > On 11/10/2015 4:08 PM, Eric Dumazet wrote: > >On Tue, 2015-11-10 at 14:41 -0800, Yang Shi wrote: > >>aarch64 doesn't have native support for XADD instruction, implement it by > >>the below instruction sequence: > >> > >>Load (dst + off)