[PATCH tip/core/rcu 09/19] scftorture: Add smp_call_function() memory-ordering checks

paulmck
2020-08-31T18:08:05Z

This commit adds checks for memory misordering across calls to and
returns from smp_call_function() in the case where the caller waits.
Misordering results in a splat.

Note that in contrast to smp_call_function_single(), this code does not
test memory ordering into the handler in the no-wait case because none
of the handlers would be able to free the scf_check structure without
introducing heavy synchronization to work out which was last.

[ paulmck: s/GFP_KERNEL/GFP_ATOMIC/ per kernel test robot feedback. ]
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
kernel/scftorture.c | 25 +++++++++++++++++--------
1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/kernel/scftorture.c b/kernel/scftorture.c
index 3519ad1..0d7299d 100644
--- a/kernel/scftorture.c
+++ b/kernel/scftorture.c
@@ -297,11 +297,13 @@ static void scftorture_invoke_one(struct scf_statistics *scfp, struct torture_ra
cpus_read_lock();
else
preempt_disable();
- switch (scfsp->scfs_prim) {
- case SCF_PRIM_SINGLE:
+ if (scfsp->scfs_prim == SCF_PRIM_SINGLE || scfsp->scfs_wait) {
scfcp = kmalloc(sizeof(*scfcp), GFP_ATOMIC);
if (WARN_ON_ONCE(!scfcp))
atomic_inc(&n_alloc_errs);
+ }
+ switch (scfsp->scfs_prim) {
+ case SCF_PRIM_SINGLE:
cpu = torture_random(trsp) % nr_cpu_ids;
if (scfsp->scfs_wait)
scfp->n_single_wait++;
@@ -328,11 +330,6 @@ static void scftorture_invoke_one(struct scf_statistics *scfp, struct torture_ra
}
break;
case SCF_PRIM_MANY:
- if (scfsp->scfs_wait) {
- scfcp = kmalloc(sizeof(*scfcp), GFP_ATOMIC);
- if (WARN_ON_ONCE(!scfcp))
- atomic_inc(&n_alloc_errs);
- }
if (scfsp->scfs_wait)
scfp->n_many_wait++;
else
@@ -356,7 +353,19 @@ static void scftorture_invoke_one(struct scf_statistics *scfp, struct torture_ra
scfp->n_all_wait++;
else
scfp->n_all++;
- smp_call_function(scf_handler, NULL, scfsp->scfs_wait);
+ if (scfcp) {
+ scfcp->scfc_cpu = -1;
+ scfcp->scfc_wait = true;
+ scfcp->scfc_out = false;
+ scfcp->scfc_in = true;
+ }
+ smp_call_function(scf_handler, scfcp, scfsp->scfs_wait);
+ if (scfcp) {
+ if (WARN_ON_ONCE(!scfcp->scfc_out))
+ atomic_inc(&n_mb_out_errs); // Leak rather than trash!
+ else
+ kfree(scfcp);
+ }
break;
}
if (use_cpus_read_lock)
--
2.9.5