> On Mon, 2011-03-07 at 16:18 -0800, James Bottomley wrote: > > On Mon, 2011-03-07 at 15:54 -0800, Bhanu Gollapudi wrote: > > > On Mon, 2011-03-07 at 12:16 -0800, Mariusz Kozlowski wrote: > > > > On Wed, Mar 02, 2011 at 11:10:03PM +0100, Mariusz Kozlowski wrote: > > > > > drivers/scsi/bnx2fc/bnx2fc_fcoe.c:1815: error: dereferencing > pointer to incomplete type > > > > > drivers/scsi/bnx2fc/bnx2fc_fcoe.c:1815: error: > âMODULE_STATE_LIVEâ undeclared (first use in this function) > > > > > > > > Hm. Still there in next-20110307. Is this patch wrong or..? > > > > > > > > > > James, > > > > > > Here is my ack for this patch. > > > > OK, so the patch is actually wrong because adding #ifdefs on modules in > > files really impedes readability. The bug is using a direct deref on > > module state instead of one of the APIs which work in the non-modular > > case, namely try_module_get(). That means the other two need to come > out > > and be reworked (plus all the others in fcoe). > > > > Reworked looks like it might be a bigger item than bnx2fc. If any of > > those tests is ever relevant, it means we have a race in the > > fcoe_transport because it shouldn't be calling function pointers on a > > dying module (unless it wants to trigger an oops). > > > > So, why are you trying to do this in the first place? > > > First, fcoe.c started with these checks. Here is a comment in fcoe.c at > the point of one of the checks. > > /* > * Make sure the module has been initialized, and is not about to be > * removed. Module paramter sysfs files are writable before the > * module_init function is called and after module_exit. > */ > > I don't know the correct way to fix that race is, but we may be past the > need to fix it in the LLDs. > > Next, the fcoe transport was added. Since it (libfcoe.ko) is now calling > what used to be the fcoe.ko sysfs entry points I don't think the problem > exists in fcoe.c or in bnx2fc_fcoe.c, the problem should be in the fcoe > transport code, as James suggested. > > The fcoe transport code already has these checks to protect against > sysfs files being writable before module initialization is complete. It > uses the ft_mutex to protect the list of transports(LLDs) so when > 'create' is called it knows that the transport is still there to call > down to. It holds the ft_mutex until the LLD's 'create' routine returns. > The transports(LLDs) should be detaching themselves from the fcoe > transport layer before they exit. fcoe_transport_detach will try to > acquire the ft_mutex and block until the 'create' call returns and > releases the ft_mutex. I think this ensures that the transport(LLD) will > be fine when the fcoe transport calls it. > > My feeling is that these checks are still needed in the fcoe transport, > but not in the LLDs. If someone can suggest a better way to protect > against writable sysfs files when the module hasn't finished > initializing, we should do that instead of the ifdefs. > > Hope this helps, > > //Rob > > FYI: mnc asked about this code and the trylock code in fcoe and libfcoe. > I have patches in our internal validation to remove the trylock usage, > but I don't have patches to fix the module state checking. > Yeah, this logic was from original fixing race condition in fcoe.ko, note that we do need check the MODULE_STATE_LIVE, try_module_get() is not what we wanted, plus module_is_live () checks if it is !GOING. Anyway, I don't think this is needed any more for individual fcoe transport driver, e.g., fcoe.ko or bnx2fc, as the race is now for sysfs of libfcoe. I will send out a patch to clean up the fcoe.c for this. Thanks, yi > -- > 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 ÿô.nlj·Ÿ®‰†+%ŠË±é¥Šwÿº{.nlj·¥Š{±þw±·ø¡Ü}©ž²ÆzÚj:+v‰¨þø®w¥þŠàÞ¨è&¢)ß«a¶Úÿûz¹ÞúŽŠÝjÿŠwèf
