On Fri, 2010-09-10 at 08:32 +0200, Jiri Slaby wrote: > On 09/09/2010 11:29 PM, Nicholas A. Bellinger wrote: > > From: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx> > > > > Greetings all, > > > > This patch converts the following functions from within shutdown and release > > path code to use cpu_relax() instead of msleep() while doing atomic_read() in > > a tight loop waiting for various PR and MIB reference count(s) to return to zero: > > > > *) core_update_device_list_for_node() + struct se_dev_entry->pr_ref_count > > *) core_release_port() + struct se_port->sep_tg_pt_ref_cnt > > *) se_dev_stop() + struct se_hba->dev_mib_access_count > > *) __core_scsi3_free_registration() + struct t10_pr_registration->pr_res_holders > > *) core_tpg_wait_for_nacl_pr_ref() + struct se_node_acl->acl_pr_ref_count > > *) core_tpg_wait_for_mib_ref() + struct se_node_acl->mib_ref_count > > *) core_tpg_deregister() + struct se_portal_group->tpg_pr_ref_count > > *) transport_deregister_session() + struct se_session->mib_ref_count > > > > Thanks to Konrad Rzeszutek Wilk for mentioning cpu_relax() usage! > > > > Signed-off-by: Nicholas A. Bellinger <nab@xxxxxxxxxxxxxxx> > > --- > > drivers/target/target_core_device.c | 6 +++--- > > drivers/target/target_core_pr.c | 2 +- > > drivers/target/target_core_tpg.c | 6 +++--- > > drivers/target/target_core_transport.c | 2 +- > > 4 files changed, 8 insertions(+), 8 deletions(-) > > > > diff --git a/drivers/target/target_core_device.c b/drivers/target/target_core_device.c > > index 665b8e2..459f0f8 100644 > > --- a/drivers/target/target_core_device.c > > +++ b/drivers/target/target_core_device.c > > @@ -532,7 +532,7 @@ int core_update_device_list_for_node( > > */ > > spin_unlock_irq(&nacl->device_list_lock); > > while (atomic_read(&deve->pr_ref_count) != 0) > > - msleep(100); > > + cpu_relax(); > > spin_lock_irq(&nacl->device_list_lock); > > /* > > * Disable struct se_dev_entry LUN ACL mapping > > Why would you want to convert those to busy-waiting? This should rather > be converted to wait_event/wake_up, right? Hi Jiri, I agree that this is the one scenario within the msleep() -> cpu_relax() conversion patch that involves something besides a simple shortly held 'non CDB I/O emulation path context ref/deref', and might probably be better served by using wait_event/wake_up. I will take a look at a conversion to use wait_queue_head_t in the near future. Thanks for your comments Jiri! --nab -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
