On 5/19/2022 5:08 PM, duoming@xxxxxxxxxx wrote:
Hello,
On Thu, 19 May 2022 08:48:44 -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()/dev_coredumpm() also cannot be called from an atomic
context and hence their gfp param is pointless and should presumably be
removed.
/jeff
