Hi, > From: Behme Dirk (CM/ESO2), Sent: Friday, October 13, 2023 3:05 PM > > Hi, > > On 12.10.2023 10:39, Yoshihiro Shimoda wrote: > > Hello Behme, > > > >> From: Behme Dirk (CM/ESO2), Sent: Tuesday, October 10, 2023 9:59 PM > >> > >> On 26.07.2023 05:19, Jakub Kicinski wrote: > >> ... > >>> The fact that ravb_tx_timeout_work doesn't take any locks seems much > >>> more suspicious. > >> Does anybody plan to look into this, too? > > > > I believe my fixed patch [1] resolved this issue too. > > > I'm not an expert of this driver nor the network stack, so sorry if I'm > totally wrong here ;) But somehow this answer confuses me. Let me explain: > > What you did with [1] is to stop/cancel the workqueue in ravb_close(). > That's fine. But that is at driver's close time. > > What's about driver's normal runtime? What I understood is that > ravb_tx_timeout_work() might run totally asynchronously to the rest of > the driver. And therefore needs locking/protection/synchronization if it > uses resources of the driver which are used elsewhere in the driver, too. > > I think this is exactly what is described with: > > > --- > > Simplest fix I can think of is to take a reference on the netdev before > > scheduling the work, and then check if it's still registered in the work > > itself. Wrap the timeout work in rtnl_lock() to avoid any races there. > > --- > > So, where is above done? Not at close time, but at normal run time of > the driver? Thank you very much for your detailed explanation. I understood it. ravb_tx_timeout_work() still has races between ethtool ops for instance. So, I'll make a patch for it by early next week. However, IIUC, using rtnl_lock() in ravb_tx_timeout_work() is possible to cause deadlock from cancel_work_sync() in ravb_close(). So, I'll use rtnl_trylock() instead. Best regards, Yoshihiro Shimoda > Best regards > > Dirk > > > Sergey suggested to add cancel_work_sync() into the ravb_close () [3]. > > And I investigated calltrace, and then the ravb_close() is under rtnl_lock() [4] > > like below: > > ----------------------------------------------------------------------- > > ravb_remove() calls unregister_netdev(). > > -> unregister_netdev() calls rtnl_lock() and unregister_netdevice(). > > --> unregiter_netdevice_queue() > > ---> unregiter_netdevice_many() > > ----> unregiter_netdevice_many_notify(). > > -----> dev_close_many() > > ------> __dev_close_many() > > -------> ops->ndo_stop() > > > > ravb_close() calls phy_stop() > > -> phy_state_machine() with PHY_HALTED > > --> phy_link_down() > > ---> phy_link_change() > > ----> netif_carrier_off() > > ----------------------------------------------------------------------- > > > > So, during cancel_work_sync() is waiting for canceling the workqueue in ravb_close(), > > it's under rtnl_lock() so that no additional locks are needed in ravb_tx_timeout_work(). > > > > [1] > https://git.kernel.org/pub/scm/linux/kernel/git%25 > 2Fnetdev%2Fnet.git%2Fcommit%2F%3Fid%3D3971442870713de527684398416970cf025b4f89&data=05%7C01%7Cyoshihiro.shimoda.uh%4 > 0renesas.com%7C466e046b20b548b264f808dbcbb255f6%7C53d82571da1947e49cb4625a166a4a2a%7C0%7C0%7C638327739033548199%7CUn > known%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=HkA8f5a > gawjXMvAGkaE6tELaSpjpbIn7M3mU5xbDTD0%3D&reserved=0 > > [2] > https://lore.kernel.org/netdev/20230727164820.48c9e685 > %40kernel.org%2F&data=05%7C01%7Cyoshihiro.shimoda.uh%40renesas.com%7C466e046b20b548b264f808dbcbb255f6%7C53d82571da19 > 47e49cb4625a166a4a2a%7C0%7C0%7C638327739033548199%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTi > I6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=cGvnA8WqxM%2FUDa%2FNS2OBztr1IWgjCX4IzBYXe1LGkZU%3D&reserved=0 > > [3] > https://lore.kernel.org/netdev/607f4fe4-5a59-39dd-71c2 > -0cf769b48187%40omp.ru%2F&data=05%7C01%7Cyoshihiro.shimoda.uh%40renesas.com%7C466e046b20b548b264f808dbcbb255f6%7C53d > 82571da1947e49cb4625a166a4a2a%7C0%7C0%7C638327739033548199%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luM > zIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=OWwBKy%2Fdckgo3clPPfn2hxE4H6ToyqdcbhPhGoqoo30%3D&reserved=0 > > [4] > https://lore.kernel.org/netdev/OSYPR01MB53341CFDBB49A3 > BA41A6752CD8F9A%40OSYPR01MB5334.jpnprd01.prod.outlook.com%2F&data=05%7C01%7Cyoshihiro.shimoda.uh%40renesas.com%7C466 > e046b20b548b264f808dbcbb255f6%7C53d82571da1947e49cb4625a166a4a2a%7C0%7C0%7C638327739033548199%7CUnknown%7CTWFpbGZsb3 > d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=Jfypf10jiUfTqWUAukjnPzIQp > urx7m0ETF5N2Toq8wE%3D&reserved=0 > > > > Best regards, > > Yoshihiro Shimoda > > > >> Best regards > >> > >> Dirk > > -- > ====================================================================== > Dirk Behme Robert Bosch Car Multimedia GmbH > CM/ESO2 > Phone: +49 5121 49-3274 Dirk Behme > Fax: +49 711 811 5053274 PO Box 77 77 77 > mailto:dirk.behme@xxxxxxxxxxxx D-31132 Hildesheim - Germany > > Bosch Group, Car Multimedia (CM) > Engineering SW Operating Systems 2 (ESO2) > > Robert Bosch Car Multimedia GmbH - Ein Unternehmen der Bosch Gruppe > Sitz: Hildesheim > Registergericht: Amtsgericht Hildesheim HRB 201334 > Aufsichtsratsvorsitzender: Dr. Dirk Hoheisel > Geschäftsführung: Dr. Steffen Berns; > Dr. Sven Ost, Jörg Pollak, Dr. Walter Schirm > ======================================================================
