On Mon, 2015-01-05 at 12:03 +0100, Bart Van Assche wrote: > Avoid that the following warning is reported when a SCSI LLD kernel > module is unloaded: > > WARNING: CPU: 5 PID: 228 at kernel/module.c:954 module_put+0x207/0x220() > Call Trace: > [<ffffffff814d1fcf>] dump_stack+0x4c/0x65 > [<ffffffff81053ada>] warn_slowpath_common+0x8a/0xc0 > [<ffffffff81053bca>] warn_slowpath_null+0x1a/0x20 > [<ffffffff810d0507>] module_put+0x207/0x220 > [<ffffffffa000bea8>] scsi_device_put+0x48/0x50 [scsi_mod] > [<ffffffffa03676d2>] scsi_disk_put+0x32/0x50 [sd_mod] > [<ffffffffa0368d4c>] sd_shutdown+0x8c/0x150 [sd_mod] > [<ffffffffa0368e79>] sd_remove+0x69/0xc0 [sd_mod] > [<ffffffff813457ef>] __device_release_driver+0x7f/0xf0 > [<ffffffff81345885>] device_release_driver+0x25/0x40 > [<ffffffff81345134>] bus_remove_device+0x124/0x1b0 > [<ffffffff8134189e>] device_del+0x13e/0x250 > [<ffffffffa001cdcd>] __scsi_remove_device+0xcd/0xe0 [scsi_mod] > [<ffffffffa001b39f>] scsi_forget_host+0x6f/0x80 [scsi_mod] > [<ffffffffa000d5f6>] scsi_remove_host+0x86/0x140 [scsi_mod] > [<ffffffffa07d5c0b>] srp_remove_work+0x9b/0x210 [ib_srp] > [<ffffffff8106fd28>] process_one_work+0x1d8/0x780 > [<ffffffff810703eb>] worker_thread+0x11b/0x4a0 > [<ffffffff81075a6f>] kthread+0xef/0x110 > [<ffffffff814dad6c>] ret_from_fork+0x7c/0xb0 > > See also patch "module: Remove stop_machine from module unloading" > (Masami Hiramatsu; commit e513cc1c07e2; kernel v3.19-rc1). > > Signed-off-by: Bart Van Assche <[email protected]> > Cc: Christoph Hellwig <[email protected]> > Cc: Hannes Reinecke <[email protected]> > --- > drivers/scsi/hosts.c | 1 + > drivers/scsi/scsi.c | 13 ++++--------- > include/scsi/scsi_host.h | 3 +++ > 3 files changed, 8 insertions(+), 9 deletions(-) > > diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c > index 8bb173e..e9155d0 100644 > --- a/drivers/scsi/hosts.c > +++ b/drivers/scsi/hosts.c > @@ -380,6 +380,7 @@ struct Scsi_Host *scsi_host_alloc(struct > scsi_host_template *sht, int privsize) > > shost->host_lock = &shost->default_lock; > spin_lock_init(shost->host_lock); > + atomic_set(&shost->module_refcnt, 0); > shost->shost_state = SHOST_CREATED; > INIT_LIST_HEAD(&shost->__devices); > INIT_LIST_HEAD(&shost->__targets); > diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c > index e028854..ed325d1 100644 > --- a/drivers/scsi/scsi.c > +++ b/drivers/scsi/scsi.c > @@ -988,7 +988,8 @@ int scsi_device_get(struct scsi_device *sdev) > return -ENXIO; > /* We can fail this if we're doing SCSI operations > * from module exit (like cache flush) */ > - try_module_get(sdev->host->hostt->module); > + if (try_module_get(sdev->host->hostt->module)) > + atomic_inc(&sdev->host->module_refcnt); > > return 0; > } > @@ -1004,14 +1005,8 @@ EXPORT_SYMBOL(scsi_device_get); > */ > void scsi_device_put(struct scsi_device *sdev) > { > -#ifdef CONFIG_MODULE_UNLOAD > - struct module *module = sdev->host->hostt->module; > - > - /* The module refcount will be zero if scsi_device_get() > - * was called from a module removal routine */ > - if (module && module_refcount(module) != 0) > - module_put(module); > -#endif > + if (atomic_dec_if_positive(&sdev->host->module_refcnt) >= 0) > + module_put(sdev->host->hostt->module); > put_device(&sdev->sdev_gendev); > } > EXPORT_SYMBOL(scsi_device_put); > diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h > index 019e668..b8e6f01 100644 > --- a/include/scsi/scsi_host.h > +++ b/include/scsi/scsi_host.h > @@ -566,6 +566,9 @@ struct Scsi_Host { > struct scsi_host_template *hostt; > struct scsi_transport_template *transportt; > > + /* Number of LLD kernel module references held by the SCSI core. */ > + atomic_t module_refcnt; > + > /* > * Area to keep a shared tag map (if needed, will be > * NULL if not).
This is a bit over coded for a fix. We don't need to duplicate the module reference, merely take into account that in the remove code module_refcnt() can now return -1, which we're not expecting. Masami, this looks like a nasty unintended consequence of commit e513cc1c07e2ab93a4514eec9833e031df3e30bb Author: Masami Hiramatsu <[email protected]> Date: Mon Nov 10 09:30:29 2014 +1030 module: Remove stop_machine from module unloading Are you sure we all should have to alter our module refcounting in removal routines like this? I think the better fix is having module_refcount() never return a negative number: unsigned long module_refcount(struct module *mod) { unsigned long ret = (unsigned long)atomic_read(&mod->refcnt); if (ret == 0) return ret return ret - MODULE_REF_BASE; } James --- diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c index e028854..90dcb2f 100644 --- a/drivers/scsi/scsi.c +++ b/drivers/scsi/scsi.c @@ -1009,7 +1009,7 @@ void scsi_device_put(struct scsi_device *sdev) /* The module refcount will be zero if scsi_device_get() * was called from a module removal routine */ - if (module && module_refcount(module) != 0) + if (module && module_refcount(module) > 0) module_put(module); #endif put_device(&sdev->sdev_gendev);
