LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Song Liu <songliubraving@fb.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "open list:BPF (Safe dynamic programs and tools)" 
	<bpf@vger.kernel.org>, LKML <linux-kernel@vger.kernel.org>,
	"acme@kernel.org" <acme@kernel.org>,
	"mingo@redhat.com" <mingo@redhat.com>,
	"kjain@linux.ibm.com" <kjain@linux.ibm.com>,
	Kernel Team <Kernel-team@fb.com>
Subject: Re: [PATCH v2 bpf-next 1/3] perf: enable branch record for software events
Date: Mon, 30 Aug 2021 17:41:46 +0000	[thread overview]
Message-ID: <719D2DC2-CC5D-4C6A-94F4-DBCADDA291CC@fb.com> (raw)
In-Reply-To: <20210830102258.GI4353@worktop.programming.kicks-ass.net>



> On Aug 30, 2021, at 3:22 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> 
> On Thu, Aug 26, 2021 at 03:13:04PM -0700, Song Liu wrote:
>> +int dummy_perf_snapshot_branch_stack(struct perf_branch_snapshot *br_snapshot);
>> +
>> +DECLARE_STATIC_CALL(perf_snapshot_branch_stack, dummy_perf_snapshot_branch_stack);
>> +
>> #endif /* _LINUX_PERF_EVENT_H */
>> diff --git a/kernel/events/core.c b/kernel/events/core.c
>> index 011cc5069b7ba..c53fe90e630ac 100644
>> --- a/kernel/events/core.c
>> +++ b/kernel/events/core.c
>> @@ -13437,3 +13437,6 @@ struct cgroup_subsys perf_event_cgrp_subsys = {
>> 	.threaded	= true,
>> };
>> #endif /* CONFIG_CGROUP_PERF */
>> +
>> +DEFINE_STATIC_CALL_NULL(perf_snapshot_branch_stack,
>> +			dummy_perf_snapshot_branch_stack);
> 
> This isn't right...
> 
> The whole dummy_perf_snapshot_branch_stack() thing is a declaration only
> and used as a typedef. Also, DEFINE_STATIC_CALL_NULL() and
> static_call_cond() rely on a void return value, which it doesn't have.
> 
> Did you want:
> 
>  DECLARE_STATIC_CALL(perf_snapshot_branch_stack, void (*)(struct perf_branch_snapshot *));
> 
>  DEFINE_STATIC_CALL_NULL(perf_snapshot_branch_stack, void (*)(struct perf_branch_snapshot *));
> 
>  static_call_cond(perf_snapshot_branch_stack)(...);
> 
> *OR*, do you actually need that return value, in which case you're
> probably looking for:
> 
>  DECLARE_STATIC_CALL(perf_snapshot_branch_stack, int (*)(struct perf_branch_snapshot *));
> 
>  DEFINE_STATIC_CALL_RET0(perf_snapshot_branch_stack, int (*)(struct perf_branch_snapshot *));
> 
>  ret = static_call(perf_snapshot_branch_stack)(...);
> 
> ?

Hmmm... something doesn't work here. I have:

/* include/linux/perf_event.h */
DECLARE_STATIC_CALL(perf_snapshot_branch_stack,
                   int (*)(struct perf_branch_snapshot *));


/* kernel/events/core.c */
DEFINE_STATIC_CALL_RET0(perf_snapshot_branch_stack,
                       int (*)(struct perf_branch_snapshot *));

/* kernel/bpf/trampoline.c */
       if (prog->call_get_branch)
               static_call(perf_snapshot_branch_stack)(
                       this_cpu_ptr(&bpf_perf_branch_snapshot));

/* arch/x86/events/intel/core.c */
       if (x86_pmu.disable_all == intel_pmu_disable_all)
               static_call_update(perf_snapshot_branch_stack,
                                  intel_pmu_snapshot_branch_stack);

And the compiler keeps complain with:

arch/x86/events/intel/core.c: In function ‘intel_pmu_init’:
./include/linux/static_call.h:121:41: error: initialization of ‘int (**)(struct perf_branch_snapshot *)’ from incompatible pointer type ‘int (*)(struct perf_branch_snapshot *)’ [-Werror=incompatible-pointer-type ]
  typeof(&STATIC_CALL_TRAMP(name)) __F = (func);   \
                                         ^
arch/x86/events/intel/core.c:6305:4: note: in expansion of macro ‘static_call_update’
    static_call_update(perf_snapshot_branch_stack,
    ^~~~~~~~~~~~~~~~~~


Something like 

typedef int (perf_snapshot_branch_stack_t)(struct perf_branch_snapshot *);
DECLARE_STATIC_CALL(perf_snapshot_branch_stack, perf_snapshot_branch_stack_t);

seems to work fine. 

Thanks,
Song


  parent reply	other threads:[~2021-08-30 17:42 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-26 22:13 [PATCH v2 bpf-next 0/3] bpf: introduce bpf_get_branch_snapshot Song Liu
2021-08-26 22:13 ` [PATCH v2 bpf-next 1/3] perf: enable branch record for software events Song Liu
2021-08-30 10:22   ` Peter Zijlstra
2021-08-30 15:25     ` Song Liu
2021-08-30 16:06       ` Peter Zijlstra
2021-08-30 16:36         ` Song Liu
2021-09-01 17:09           ` Peter Zijlstra
2021-08-30 17:41     ` Song Liu [this message]
2021-08-30 18:07       ` Peter Zijlstra
2021-09-01 17:12         ` Peter Zijlstra
2021-09-04 23:01           ` Josh Poimboeuf
2021-08-30 10:43   ` Peter Zijlstra
2021-08-30 16:06     ` Song Liu
2021-08-26 22:13 ` [PATCH v2 bpf-next 2/3] bpf: introduce helper bpf_get_branch_snapshot Song Liu
2021-08-27  9:28   ` kernel test robot
2021-08-27 15:10   ` kernel test robot
2021-08-30 10:47     ` Peter Zijlstra
2021-08-26 22:13 ` [PATCH v2 bpf-next 3/3] selftests/bpf: add test for bpf_get_branch_snapshot Song Liu

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=719D2DC2-CC5D-4C6A-94F4-DBCADDA291CC@fb.com \
    --to=songliubraving@fb.com \
    --cc=Kernel-team@fb.com \
    --cc=acme@kernel.org \
    --cc=bpf@vger.kernel.org \
    --cc=kjain@linux.ibm.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@redhat.com \
    --cc=peterz@infradead.org \
    --subject='Re: [PATCH v2 bpf-next 1/3] perf: enable branch record for software events' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).