On 7/7/23 12:16, Paul E. McKenney wrote:
On Fri, Jul 07, 2023 at 10:56:51AM -0400, Waiman Long wrote:
On 7/7/23 10:07, Davidlohr Bueso wrote:
On Thu, 06 Jul 2023, Waiman Long wrote:
It was found that running the refscale test might sometimes crash the
kernel with the following error:
[ 8569.952896] BUG: unable to handle page fault for address:
ffffffffffffffe8
[ 8569.952900] #PF: supervisor read access in kernel mode
[ 8569.952902] #PF: error_code(0x0000) - not-present page
[ 8569.952904] PGD c4b048067 P4D c4b049067 PUD c4b04b067 PMD 0
[ 8569.952910] Oops: 0000 [#1] PREEMPT_RT SMP NOPTI
[ 8569.952916] Hardware name: Dell Inc. PowerEdge R750/0WMWCR, BIOS
1.2.4 05/28/2021
[ 8569.952917] RIP: 0010:prepare_to_wait_event+0x101/0x190
:
[ 8569.952940] Call Trace:
[ 8569.952941] <TASK>
[ 8569.952944] ref_scale_reader+0x380/0x4a0 [refscale]
[ 8569.952959] kthread+0x10e/0x130
[ 8569.952966] ret_from_fork+0x1f/0x30
[ 8569.952973] </TASK>
This is likely caused by the fact that init_waitqueue_head() is called
after the ref_scale_reader kthread is created. So the kthread may try
to use the waitqueue head before it is properly initialized. Fix this
by initializing the waitqueue head first before kthread creation.
Fixes: 653ed64b01dc ("refperf: Add a test to measure performance of
read-side synchronization")
Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
Strange this wasn't reported sooner.
Red Hat does have a pretty large QE organization that run all sort of tests
include this one pretty frequently. The race window is pretty small, but
they did hit this once in a while.
I do run this fairly frequently, but haven't managed to hit it.
Good show on making it happen, and looking forward to the updated patch!
v2 sent with a bit more explanation text in the commit log.
Cheers,
Longman
