#include <sched.h>
#include "util.h"
#include "../perf.h"
#include "cloexec.h"
#include "asm/bug.h"
#include "debug.h"
#include <unistd.h>
#include <asm/unistd.h>
#include <sys/syscall.h>

static unsigned long flag = PERF_FLAG_FD_CLOEXEC;

int __weak sched_getcpu(void)
{
#ifdef __NR_getcpu
	unsigned cpu;
	int err = syscall(__NR_getcpu, &cpu, NULL, NULL);
	if (!err)
		return cpu;
#else
	errno = ENOSYS;
#endif
	return -1;
}

static int perf_flag_probe(void)
{
	/* use 'safest' configuration as used in perf_evsel__fallback() */
	struct perf_event_attr attr = {
		.type = PERF_TYPE_SOFTWARE,
		.config = PERF_COUNT_SW_CPU_CLOCK,
		.exclude_kernel = 1,
	};
	int fd;
	int err;
	int cpu;
	pid_t pid = -1;
	char sbuf[STRERR_BUFSIZE];

	cpu = sched_getcpu();
	if (cpu < 0)
		cpu = 0;

	/*
	 * Using -1 for the pid is a workaround to avoid gratuitous jump label
	 * changes.
	 */
	while (1) {
		/* check cloexec flag */
		fd = sys_perf_event_open(&attr, pid, cpu, -1,
					 PERF_FLAG_FD_CLOEXEC);
		if (fd < 0 && pid == -1 && errno == EACCES) {
			pid = 0;
			continue;
		}
		break;
	}
	err = errno;

	if (fd >= 0) {
		close(fd);
		return 1;
	}

	WARN_ONCE(err != EINVAL && err != EBUSY,
		  "perf_event_open(..., PERF_FLAG_FD_CLOEXEC) failed with unexpected error %d (%s)\n",
		  err, str_error_r(err, sbuf, sizeof(sbuf)));

	/* not supported, confirm error related to PERF_FLAG_FD_CLOEXEC */
	while (1) {
		fd = sys_perf_event_open(&attr, pid, cpu, -1, 0);
		if (fd < 0 && pid == -1 && errno == EACCES) {
			pid = 0;
			continue;
		}
		break;
	}
	err = errno;

	if (fd >= 0)
		close(fd);

	if (WARN_ONCE(fd < 0 && err != EBUSY,
		      "perf_event_open(..., 0) failed unexpectedly with error %d (%s)\n",
		      err, str_error_r(err, sbuf, sizeof(sbuf))))
		return -1;

	return 0;
}

unsigned long perf_event_open_cloexec_flag(void)
{
	static bool probed;

	if (!probed) {
		if (perf_flag_probe() <= 0)
			flag = 0;
		probed = true;
	}

	return flag;
}
e/br_sysfs_br.c?id=15c2e102412d95af4fe88e5b28b3eba124545bbf'>commit</a><a href='/cgit.cgi/linux/net-next.git/diff/net/bridge/br_sysfs_br.c?id=15c2e102412d95af4fe88e5b28b3eba124545bbf'>diff</a></td><td class='form'><form class='right' method='get' action='/cgit.cgi/linux/net-next.git/log/net/bridge/br_sysfs_br.c'>
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<div class='path'>path: <a href='/cgit.cgi/linux/net-next.git/log/?id=15c2e102412d95af4fe88e5b28b3eba124545bbf&amp;showmsg=1'>root</a>/<a href='/cgit.cgi/linux/net-next.git/log/net?id=15c2e102412d95af4fe88e5b28b3eba124545bbf&amp;showmsg=1'>net</a>/<a href='/cgit.cgi/linux/net-next.git/log/net/bridge?id=15c2e102412d95af4fe88e5b28b3eba124545bbf&amp;showmsg=1'>bridge</a>/<a href='/cgit.cgi/linux/net-next.git/log/net/bridge/br_sysfs_br.c?id=15c2e102412d95af4fe88e5b28b3eba124545bbf&amp;showmsg=1'>br_sysfs_br.c</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/cgit.cgi/linux/net-next.git/log/net/bridge/br_sysfs_br.c?id=15c2e102412d95af4fe88e5b28b3eba124545bbf'>Collapse</a>)</th><th class='left'>Author</th><th class='left'>Files</th><th class='left'>Lines</th></tr>
<tr class='logheader'><td><span title='2017-02-06 22:53:13 -0500'>2017-02-06</span></td><td class='logsubject'><a href='/cgit.cgi/linux/net-next.git/commit/net/bridge/br_sysfs_br.c?id=f7cdee8a79a1cb03fa9ca71b825e72f880b344e1'>bridge: move to workqueue gc</a></td><td>Nikolay Aleksandrov</td><td>1</td><td><span class='deletions'>-1</span>/<span class='insertions'>+1</span></td></tr>
<tr class='nohover-highlight'><td/><td colspan='5' class='logmsg'>
Move the fdb garbage collector to a workqueue which fires at least 10
milliseconds apart and cleans chain by chain allowing for other tasks
to run in the meantime. When having thousands of fdbs the system is much
more responsive. Most importantly remove the need to check if the
matched entry has expired in __br_fdb_get that causes false-sharing and
is completely unnecessary if we cleanup entries, at worst we'll get 10ms
of traffic for that entry before it gets deleted.

Signed-off-by: Nikolay Aleksandrov &lt;nikolay@cumulusnetworks.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;


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