duoming@xxxxxxxxxx writes: > Hello, > > On Fri, 20 May 2022 09:08:52 -0700 Jeff Johnson wrote: > >> >>>>> There are sleep in atomic context bugs when uploading device dump >> >>>>> data on usb interface. The root cause is that the operations that >> >>>>> may sleep are called in fw_dump_timer_fn which is a timer handler. >> >>>>> The call tree shows the execution paths that could lead to bugs: >> >>>>> >> >>>>> (Interrupt context) >> >>>>> fw_dump_timer_fn >> >>>>> mwifiex_upload_device_dump >> >>>>> dev_coredumpv(..., GFP_KERNEL) >> >> >> >> just looking at this description, why isn't the simple fix just to >> >> change this call to use GFP_ATOMIC? >> > >> > Because change the parameter of dev_coredumpv() to GFP_ATOMIC could only solve >> > partial problem. The following GFP_KERNEL parameters are in /lib/kobject.c >> > which is not influenced by dev_coredumpv(). >> > >> > kobject_set_name_vargs >> > kvasprintf_const(GFP_KERNEL, ...); //may sleep >> > kstrdup(s, GFP_KERNEL); //may sleep >> >> Then it seems there is a problem with dev_coredumpm(). >> >> dev_coredumpm() takes a gfp param which means it expects to be called in >> any context, but it then calls dev_set_name() which, as you point out, >> cannot be called from an atomic context. >> >> So if we cannot change the fact that dev_set_name() cannot be called >> from an atomic context, then it would seem to follow that >> dev_coredumpv also cannot be called from an atomic >> context and hence their gfp param is pointless and should presumably be >> removed. > > Thanks for your time and suggestions! I think the gfp_t parameter of dev_coredumpv and > dev_coredumpm may not be removed, because it could be used to pass value to gfp_t > parameter of kzalloc in dev_coredumpm. What's more, there are also many other places > use dev_coredumpv and dev_coredumpm, if we remove the gfp_t parameter, there are too many > places that need to modify and these places are not in interrupt > context. "Too many users" is not a valid reason to leave a bug in place, either dev_coredumpv() should support GFP_ATOMIC or the gfp_t parameter should be removed. > There are two solutions now: one is to moves the operations that may > sleep into a work item. That does not fix the root cause that dev_coredumpv() claims it can be called in atomic contexts. > Another is to change the gfp_t parameter of dev_coredumpv from GFP_KERNEL to GFP_ATOMIC, and > change the gfp_t parameter of kvasprintf_const and kstrdup from GFP_KERNEL to > "in_interrupt() ? GFP_ATOMIC : GFP_KERNEL". in_interrupt() is deprecated and should not be used. And I don't think it detects all atomic contexts like spinlocks. -- https://patchwork.kernel.org/project/linux-wireless/list/ https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches
