Merge tag 'scftorture.2023.08.15a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu

Pull smp_call_function torture-test updates from Paul McKenney:
 "This prevents some memory-exhaustion false-postitive failures in
  scftorture testing"

* tag 'scftorture.2023.08.15a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu:
  scftorture: Add CONFIG_PREEMPT_DYNAMIC=n to NOPREEMPT scenario
  scftorture: Pause testing after memory-allocation failure
  scftorture: Forgive memory-allocation failure if KASAN
  torture: Scale scftorture memory based on number of CPUs

Author: torvalds

kernel/scftorture.c

@@ -171,7 +171,8 @@ static void scf_torture_stats_print(void)
 		scfs.n_all_wait += scf_stats_p[i].n_all_wait;
 	}
 	if (atomic_read(&n_errs) || atomic_read(&n_mb_in_errs) ||
-	    atomic_read(&n_mb_out_errs) || atomic_read(&n_alloc_errs))
+	    atomic_read(&n_mb_out_errs) ||
+	    (!IS_ENABLED(CONFIG_KASAN) && atomic_read(&n_alloc_errs)))
 		bangstr = "!!! ";
 	pr_alert("%s %sscf_invoked_count %s: %lld resched: %lld single: %lld/%lld single_ofl: %lld/%lld single_rpc: %lld single_rpc_ofl: %lld many: %lld/%lld all: %lld/%lld ",
 		 SCFTORT_FLAG, bangstr, isdone ? "VER" : "ver", invoked_count, scfs.n_resched,
@@ -312,6 +313,7 @@ static void scf_handler_1(void *scfc_in)
 // Randomly do an smp_call_function*() invocation.
 static void scftorture_invoke_one(struct scf_statistics *scfp, struct torture_random_state *trsp)
 {
+	bool allocfail = false;
 	uintptr_t cpu;
 	int ret = 0;
 	struct scf_check *scfcp = NULL;
@@ -323,8 +325,10 @@ static void scftorture_invoke_one(struct scf_statistics *scfp, struct torture_ra
 		preempt_disable();
 	if (scfsp->scfs_prim == SCF_PRIM_SINGLE || scfsp->scfs_wait) {
 		scfcp = kmalloc(sizeof(*scfcp), GFP_ATOMIC);
-		if (WARN_ON_ONCE(!scfcp)) {
+		if (!scfcp) {
+			WARN_ON_ONCE(!IS_ENABLED(CONFIG_KASAN));
 			atomic_inc(&n_alloc_errs);
+			allocfail = true;
 		} else {
 			scfcp->scfc_cpu = -1;
 			scfcp->scfc_wait = scfsp->scfs_wait;
@@ -431,7 +435,9 @@ static void scftorture_invoke_one(struct scf_statistics *scfp, struct torture_ra
 		cpus_read_unlock();
 	else
 		preempt_enable();
-	if (!(torture_random(trsp) & 0xfff))
+	if (allocfail)
+		schedule_timeout_idle((1 + longwait) * HZ);  // Let no-wait handlers complete.
+	else if (!(torture_random(trsp) & 0xfff))
 		schedule_timeout_uninterruptible(1);
 }
 

tools/testing/selftests/rcutorture/bin/torture.sh

@@ -424,8 +424,10 @@ fi
 
 if test "$do_scftorture" = "yes"
 then
+	# Scale memory based on the number of CPUs.
+	scfmem=$((2+HALF_ALLOTED_CPUS/16))
 	torture_bootargs="scftorture.nthreads=$HALF_ALLOTED_CPUS torture.disable_onoff_at_boot csdlock_debug=1"
-	torture_set "scftorture" tools/testing/selftests/rcutorture/bin/kvm.sh --torture scf --allcpus --duration "$duration_scftorture" --configs "$configs_scftorture" --kconfig "CONFIG_NR_CPUS=$HALF_ALLOTED_CPUS" --memory 2G --trust-make
+	torture_set "scftorture" tools/testing/selftests/rcutorture/bin/kvm.sh --torture scf --allcpus --duration "$duration_scftorture" --configs "$configs_scftorture" --kconfig "CONFIG_NR_CPUS=$HALF_ALLOTED_CPUS" --memory ${scfmem}G --trust-make
 fi
 
 if test "$do_rt" = "yes"

tools/testing/selftests/rcutorture/configs/scf/NOPREEMPT

@@ -2,6 +2,8 @@ CONFIG_SMP=y
 CONFIG_PREEMPT_NONE=y
 CONFIG_PREEMPT_VOLUNTARY=n
 CONFIG_PREEMPT=n
+CONFIG_PREEMPT_DYNAMIC=n
+#CHECK#CONFIG_PREEMPT_RCU=n
 CONFIG_HZ_PERIODIC=n
 CONFIG_NO_HZ_IDLE=n
 CONFIG_NO_HZ_FULL=y