scftorture: Add smp_call_function() memory-ordering checks

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>

diff --git a/kernel/scftorture.c b/kernel/scftorture.c
index 3519ad1b3278c10d764e8187e6233e823f484ca2..0d7299d32dd085f50929deb25972857f9cc2a1c8 100644 (file)
--- 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)