diff options
author | Daniel Jordan <[email protected]> | 2019-07-16 12:32:53 -0400 |
---|---|---|
committer | Herbert Xu <[email protected]> | 2019-07-18 13:39:54 +0800 |
commit | cf144f81a99d1a3928f90b0936accfd3f45c9a0a (patch) | |
tree | 67358b6e33bbd9bb76d657673f69cb82bb6ab0b6 /lib/mpi | |
parent | 83bf42510d7f7e1daa692c096e8e9919334d7b57 (diff) |
padata: use smp_mb in padata_reorder to avoid orphaned padata jobs
Testing padata with the tcrypt module on a 5.2 kernel...
# modprobe tcrypt alg="pcrypt(rfc4106(gcm(aes)))" type=3
# modprobe tcrypt mode=211 sec=1
...produces this splat:
INFO: task modprobe:10075 blocked for more than 120 seconds.
Not tainted 5.2.0-base+ #16
modprobe D 0 10075 10064 0x80004080
Call Trace:
? __schedule+0x4dd/0x610
? ring_buffer_unlock_commit+0x23/0x100
schedule+0x6c/0x90
schedule_timeout+0x3b/0x320
? trace_buffer_unlock_commit_regs+0x4f/0x1f0
wait_for_common+0x160/0x1a0
? wake_up_q+0x80/0x80
{ crypto_wait_req } # entries in braces added by hand
{ do_one_aead_op }
{ test_aead_jiffies }
test_aead_speed.constprop.17+0x681/0xf30 [tcrypt]
do_test+0x4053/0x6a2b [tcrypt]
? 0xffffffffa00f4000
tcrypt_mod_init+0x50/0x1000 [tcrypt]
...
The second modprobe command never finishes because in padata_reorder,
CPU0's load of reorder_objects is executed before the unlocking store in
spin_unlock_bh(pd->lock), causing CPU0 to miss CPU1's increment:
CPU0 CPU1
padata_reorder padata_do_serial
LOAD reorder_objects // 0
INC reorder_objects // 1
padata_reorder
TRYLOCK pd->lock // failed
UNLOCK pd->lock
CPU0 deletes the timer before returning from padata_reorder and since no
other job is submitted to padata, modprobe waits indefinitely.
Add a pair of full barriers to guarantee proper ordering:
CPU0 CPU1
padata_reorder padata_do_serial
UNLOCK pd->lock
smp_mb()
LOAD reorder_objects
INC reorder_objects
smp_mb__after_atomic()
padata_reorder
TRYLOCK pd->lock
smp_mb__after_atomic is needed so the read part of the trylock operation
comes after the INC, as Andrea points out. Thanks also to Andrea for
help with writing a litmus test.
Fixes: 16295bec6398 ("padata: Generic parallelization/serialization interface")
Signed-off-by: Daniel Jordan <[email protected]>
Cc: <[email protected]>
Cc: Andrea Parri <[email protected]>
Cc: Boqun Feng <[email protected]>
Cc: Herbert Xu <[email protected]>
Cc: Paul E. McKenney <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Steffen Klassert <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Herbert Xu <[email protected]>
Diffstat (limited to 'lib/mpi')
0 files changed, 0 insertions, 0 deletions