linux-kernel - Re: [rfc][patch] perf,tools: Remove test_attr

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Date:	Fri, 2 May 2014 13:52:01 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [rfc][patch] perf,tools: Remove test_attr_* muck from perf.h

On Thu, May 01, 2014 at 08:35:05PM +0200, Jiri Olsa wrote:
> On Thu, May 01, 2014 at 10:27:30AM +0200, Peter Zijlstra wrote:
> > Hi,
> > 
> > I occasionally build the odd program against raw perf and use perf.h for
> > this.
> > 
> > Now I find that no longer works because of:
> > 
> > 52502bf201a85 ("perf tests: Add framework for automated perf_event_attr tests")
> > 
> > So revert the hunk touching on perf.h.
> 
> But but but, then you'll brake attr tests
> 
> > 
> > Also, it seems to be for snake shit only, and snakes stink, except on a
> > plane :-)
> 
> wanna get to lwn quotes page, huh? ;)
> 
> any details about the breakage? maybe we could find some
> way to make you happy and keep the snake shit in place

linux-2.6/tools/perf# gcc -o perf_bug perf_bug.c
/tmp/cclObJsz.o: In function `sys_perf_event_open':
perf_bug.c:(.text+0x48): undefined reference to `test_attr__enabled'
perf_bug.c:(.text+0x72): undefined reference to `test_attr__open'
collect2: error: ld returned 1 exit status

Initially perf.h was meant to have just the syscall wrapper and few
system level defines (like the membars etc..)

But now its grown all kinds of gunk outside of that.

So ideally we'd split the thing into two files, one which is a
stand-alone syscall wrapper + system utils things and one which includes
the former and adds all the perf (tool, not kernel) gunk on.

I see all sorts of extern perf_{host,guest} things and util/target.h
includes.. that all should definitely move elsewhere.

---
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/mman.h>
#include <signal.h>
#include <unistd.h>
#include <stdio.h>
#include "perf.h"

struct perf_event_attr perf_attr = {
	.type = PERF_TYPE_SOFTWARE,
	.config = PERF_COUNT_SW_EMULATION_FAULTS,
	.sample_period = 0,
	.inherit = 1,
};

int main(void)
{
	void *page;
	pid_t pid;
	int fd[16];

	fd[0] = sys_perf_event_open(&perf_attr, 0, -1, -1, 0);
	if (fd[0] < 0) {
		perror("sys_perf_event_open 0");
		return 0;
	}

	perf_attr.inherit = 0;

	fd[1] = sys_perf_event_open(&perf_attr, 0, -1, fd[0], 0);
	if (fd[1] < 0) {
		perror("sys_perf_event_open 1");
		return 0;
	}

	page = mmap(NULL, 3*4096, PROT_READ|PROT_WRITE, MAP_SHARED, fd[1], 0);
	if (page == ((void *)-1)) {
		perror("mmap");
		return 0;
	}

	pid = fork();
	if (!pid) {
		/* child */
		while (1) ;
		return 0;
	}
	usleep(500000);

	munmap(page, 3*4096);

	close(fd[1]);
	kill(pid, SIGTERM);
	waitpid(pid, NULL, 0);

	return 0;
}

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