[PATCH] xfrm: avoid spinlock in get_acqseq()

[PATCH] xfrm: avoid spinlock in get_acqseq()

[Eric Dumazet]

Use atomic_inc_return() in get_acqseq() to avoid taking a spinlock

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
---

diff --git a/net/key/af_key.c b/net/key/af_key.c
index 4744b1f..e2aacf0 100644
--- a/net/key/af_key.c
+++ b/net/key/af_key.c
@@ -3019,12 +3019,11 @@ static int pfkey_send_policy_notify(struct xfrm_policy *xp, int dir, struct km_e
 static u32 get_acqseq(void)
 {
 	u32 res;
-	static u32 acqseq;
-	static DEFINE_SPINLOCK(acqseq_lock);
+	static atomic_t acqseq;
 
-	spin_lock_bh(&acqseq_lock);
-	res = (++acqseq ? : ++acqseq);
-	spin_unlock_bh(&acqseq_lock);
+	do {
+		res = atomic_inc_return(&acqseq);
+	} while (!res);
 	return res;
 }
 

Re: [PATCH] xfrm: avoid spinlock in get_acqseq()

[Benjamin LaHaise]

Hi Eric,

On Fri, Jan 29, 2010 at 03:05:52PM +0100, Eric Dumazet wrote:
> Use atomic_inc_return() in get_acqseq() to avoid taking a spinlock
> +	static atomic_t acqseq;

I think that needs to be:
	static atomic_t acqseq = ATOMIC_INIT(0);

Cheers,

	-ben

Re: [PATCH] xfrm: avoid spinlock in get_acqseq()

[Eric Dumazet]

Le vendredi 29 janvier 2010 à 10:11 -0500, Benjamin LaHaise a écrit :
> Hi Eric,
> 
> On Fri, Jan 29, 2010 at 03:05:52PM +0100, Eric Dumazet wrote:
> > Use atomic_inc_return() in get_acqseq() to avoid taking a spinlock
> > +	static atomic_t acqseq;
> 
> I think that needs to be:
> 	static atomic_t acqseq = ATOMIC_INIT(0);
> 
> Cheers,
> 
> 	-ben

Not sure its needed now that atomic_t is an integral 32bits type for all
arches, or a cleanup patch is wanted :)

Thanks !


./security/tomoyo/realpath.c:412:static atomic_t tomoyo_dynamic_memory_size;
./arch/sh/kernel/perf_event.c:41:static atomic_t num_events;
./arch/um/kernel/smp.c:199:static atomic_t scf_started;
./arch/um/kernel/smp.c:200:static atomic_t scf_finished;
./arch/ia64/kernel/mca.c:1287:	static atomic_t mca_count;
./arch/ia64/kernel/mca.c:1661:	static atomic_t slaves;
./arch/ia64/kernel/mca.c:1662:	static atomic_t monarchs;
./arch/ia64/kernel/crash.c:24:static atomic_t kdump_cpu_frozen;
./arch/x86/mm/mmio-mod.c:62:static atomic_t mmiotrace_enabled;
./arch/x86/mm/mmio-mod.c:237:	static atomic_t next_id;
./arch/x86/kernel/cpu/perf_event.c:714:static atomic_t active_events;
./arch/x86/kernel/cpu/mcheck/mce.c:238:static atomic_t mce_paniced;
./arch/x86/kernel/cpu/mcheck/mce.c:241:static atomic_t mce_fake_paniced;
./arch/x86/kernel/cpu/mcheck/mce.c:614:static atomic_t mce_executing;
./arch/x86/kernel/cpu/mcheck/mce.c:619:static atomic_t mce_callin;
./arch/x86/kernel/cpu/mcheck/mce.c:727:static atomic_t global_nwo;
./arch/x86/kernel/tboot.c:297:static atomic_t ap_wfs_count;
./arch/x86/kernel/reboot.c:724:static atomic_t waiting_for_crash_ipi;
./arch/blackfin/kernel/irqchip.c:17:static atomic_t irq_err_count;
./arch/microblaze/kernel/of_device.c:14:	static atomic_t bus_no_reg_magic;
./arch/powerpc/platforms/iseries/viopath.c:74:static atomic_t event_buffer_available[VIO_MAX_SUBTYPES];
./arch/powerpc/kernel/of_device.c:15:	static atomic_t bus_no_reg_magic;
./arch/powerpc/kernel/perf_event.c:959:static atomic_t num_events;
./mm/memcontrol.c:1283:static atomic_t memcg_drain_count;
./virt/kvm/kvm_main.c:75:static atomic_t hardware_enable_failed;
./net/netfilter/nfnetlink_log.c:71:static atomic_t global_seq;
./net/decnet/af_decnet.c:158:static atomic_t decnet_memory_allocated;
./net/llc/llc_conn.c:775:static atomic_t llc_sock_nr;
./net/core/netpoll.c:41:static atomic_t trapped;
./net/sctp/socket.c:116:static atomic_t sctp_memory_allocated;
./net/sunrpc/sched.c:238:	static atomic_t rpc_pid;
./fs/ocfs2/stack_user.c:160:static atomic_t ocfs2_control_opened;
./fs/notify/inotify/inotify.c:37:static atomic_t inotify_cookie;
./fs/notify/inotify/inotify_user.c:62:static atomic_t inotify_grp_num;
./fs/afs/rxrpc.c:20:static atomic_t afs_outstanding_calls;
./fs/afs/rxrpc.c:21:static atomic_t afs_outstanding_skbs;
./fs/afs/super.c:59:static atomic_t afs_count_active_inodes;
./fs/quota/quota.c:558:	static atomic_t seq;
./fs/dlm/user.c:29:static atomic_t dlm_monitor_opened;
./fs/ecryptfs/miscdev.c:31:static atomic_t ecryptfs_num_miscdev_opens;
./kernel/rcutree.c:1575:static atomic_t rcu_barrier_cpu_count;
./kernel/trace/trace.c:807:static atomic_t trace_record_cmdline_disabled __read_mostly;
./kernel/trace/trace_mmiotrace.c:26:static atomic_t dropped_count;
./kernel/slow-work.c:85:static atomic_t slow_work_thread_count;
./kernel/slow-work.c:86:static atomic_t vslow_work_executing_count;
./kernel/rtmutex-tester.c:24:static atomic_t rttest_event;
./kernel/async.c:83:static atomic_t entry_count;
./kernel/async.c:84:static atomic_t thread_count;
./kernel/perf_event.c:45:static atomic_t nr_events __read_mostly;
./kernel/perf_event.c:46:static atomic_t nr_mmap_events __read_mostly;
./kernel/perf_event.c:47:static atomic_t nr_comm_events __read_mostly;
./kernel/perf_event.c:48:static atomic_t nr_task_events __read_mostly;
./kernel/profile.c:42:static atomic_t *prof_buffer;
./kernel/rcutorture.c:121:static atomic_t rcu_torture_wcount[RCU_TORTURE_PIPE_LEN + 1];
./kernel/rcutorture.c:122:static atomic_t n_rcu_torture_alloc;
./kernel/rcutorture.c:123:static atomic_t n_rcu_torture_alloc_fail;
./kernel/rcutorture.c:124:static atomic_t n_rcu_torture_free;
./kernel/rcutorture.c:125:static atomic_t n_rcu_torture_mberror;
./kernel/rcutorture.c:126:static atomic_t n_rcu_torture_error;
./kernel/stop_machine.c:39:static atomic_t thread_ack;
./kernel/kgdb.c:124:static atomic_t			passive_cpu_wait[NR_CPUS];
./kernel/kgdb.c:125:static atomic_t			cpu_in_kgdb[NR_CPUS];
./kernel/time/timer_stats.c:119:static atomic_t overflow_count;
./drivers/dma/ppc4xx/adma.c:106:static atomic_t ppc440spe_adma_err_irq_ref;
./drivers/s390/cio/css.c:470:static atomic_t css_eval_scheduled;
./drivers/s390/cio/cio.c:960:static atomic_t chpid_reset_count;
./drivers/pci/hotplug/cpci_hotplug_core.c:59:static atomic_t extracting;
./drivers/char/rocket.c:114:static atomic_t rp_num_ports_open;	               /*  Number of serial ports open                           */
./drivers/char/ipmi/ipmi_msghandler.c:4044:static atomic_t stop_operation;
./drivers/md/md.c:160:static atomic_t md_event_count;
./drivers/ieee1394/raw1394.c:79:static atomic_t iso_buffer_size;
./drivers/usb/serial/io_edgeport.c:196:static atomic_t CmdUrbs;	/* Number of outstanding Command Write Urbs */
./drivers/net/pppol2tp.c:229:static atomic_t pppol2tp_tunnel_count;
./drivers/net/pppol2tp.c:230:static atomic_t pppol2tp_session_count;
./drivers/net/vmxnet3/vmxnet3_drv.c:45:static atomic_t devices_found;
./drivers/watchdog/bcm47xx_wdt.c:52:static atomic_t ticks;
./drivers/staging/batman-adv/routing.c:46:static atomic_t data_ready_cond;
./drivers/scsi/lpfc/lpfc_debugfs.c:1214:static atomic_t lpfc_debugfs_hba_count;
./drivers/scsi/scsi_transport_fc.c:484:static atomic_t fc_event_seq;
./drivers/scsi/hosts.c:43:static atomic_t scsi_host_next_hn;	/* host_no for next new host */
./drivers/scsi/scsi_transport_iscsi.c:84:static atomic_t iscsi_session_nr; /* sysfs session id for next new session */
./drivers/scsi/qla2xxx/qla_dfs.c:13:static atomic_t qla2x00_dfs_root_count;
./drivers/crypto/hifn_795x.c:54:static atomic_t hifn_dev_number;

Re: [PATCH] xfrm: avoid spinlock in get_acqseq()

[Benjamin LaHaise]

On Fri, Jan 29, 2010 at 05:00:19PM +0100, Eric Dumazet wrote:
> Not sure its needed now that atomic_t is an integral 32bits type for all
> arches, or a cleanup patch is wanted :)
> 
> Thanks !

Ah, yes, it looks like things have changed in this area a bit over time.  
I'll do up a cleanup patch for this.

		-ben

Re: [PATCH] xfrm: avoid spinlock in get_acqseq()

[David Miller]

From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Fri, 29 Jan 2010 15:05:52 +0100

> Use atomic_inc_return() in get_acqseq() to avoid taking a spinlock
> 
> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>

Applied.