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Date: Thu, 16 Jan 2014 10:04:31 -0800 From: Scott Feldman <sfeldma@...ulusnetworks.com> To: Veaceslav Falico <vfalico@...hat.com> Cc: Jay Vosburgh <fubar@...ibm.com>, Andy Gospodarek <andy@...yhouse.net>, Netdev <netdev@...r.kernel.org>, Roopa Prabhu <roopa@...ulusnetworks.com>, Shrijeet Mukherjee <shm@...ulusnetworks.com> Subject: Re: [PATCH net-next 1/2] bonding: add sysfs /slave dir for bond slave devices. On Jan 16, 2014, at 7:31 AM, Veaceslav Falico <vfalico@...hat.com> wrote: > On Wed, Jan 15, 2014 at 09:54:34PM -0800, Scott Feldman wrote: >> Add sub-directory under /sys/class/net/<interface>/slave with >> read-only attributes for slave. Directory only appears when >> <interface> is a slave. >> +static ssize_t state_show(struct slave *slave, char *buf) >> +{ >> + switch (bond_slave_state(slave)) { >> + case BOND_STATE_ACTIVE: >> + return sprintf(buf, "active\n"); >> + case BOND_STATE_BACKUP: >> + return sprintf(buf, "backup\n"); >> + default: >> + return sprintf(buf, "UNKONWN\n"); >> + } >> +} >> +static SLAVE_ATTR_RO(state); > > Am I missing something or does it really completely lacks any locking? > > What prevents the slave to be freed in between? Correct me if I’m wrong, but I think the equivalent question is: is there a race between sysfs_remove_file() and another CPU open on that file trying to read/write the file? I believe the answer is no, but I’ll defer to the experts. The file removal call path is: bond_release (ndo_del_slave) __bond_release_one bond_sysfs_slave_del sysfs_remove_file <...continue freeing slave...> So slave is freed after sysfs_remove_file. I would expect I/O on sysfs file to fail during sysfs_remove_file. Does this sound OK? Am I missing anything else? -scott -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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