linuxmsm/laptops-kernel
0
0
Fork 0
mirror of https://github.com/linux-msm/laptops-kernel.git synced 2026-08-13 14:19:53 -07:00
Code Issues Packages Projects Releases Wiki Activity

scftorture: Remove preempt_disable() in scftorture_invoke_one()

Browse Source 
The smp_call*() functions handle their required preemption and CPU
pinning internally. The explicit preempt_disable() in
scftorture_invoke_one() is therefore no longer required for correctness.
Keeping the outer preempt_disable() would also prevent scftorture from
exercising the narrowed internal preemption-disabled regions during IPI
dispatch.

Removing the outer preemption protection can expose a CPU hotplug race in
the test validation when use_cpus_read_lock is false. For multicast
operations, SCF_PRIM_MANY or SCF_PRIM_ALL, if only one CPU is online,
smp_call_function_many() correctly skips sending IPIs and leaves scfc_out
false. Without preemption disabled, a CPU hotplug thread can preempt the
test thread, bring a second CPU online and increment num_online_cpus().
When the test thread resumes, the validation check can observe
num_online_cpus() > 1 and falsely trigger the memory-ordering warning,
leaking the scfcp structure.

Remove the preempt_disable() and preempt_enable() pairs around the
smp_call*() invocations in scftorture_invoke_one(). Restrict the
num_online_cpus() > 1 validation to the use_cpus_read_lock=true case,
where the CPU count is stable during the evaluation.

Signed-off-by: Chuyi Zhou <zhouchuyi@bytedance.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Tested-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://patch.msgid.link/20260709122933.4021501-10-zhouchuyi@bytedance.com
This commit is contained in:
Chuyi Zhou
2026-07-16 09:24:56 +02:00
committed by Thomas Gleixner
parent 947c397f59
commit 99b49e02f9
1 changed files with 4 additions and 9 deletions
Download Patch File Download Diff File Expand all files Collapse all files
kernel/scftorture.c
+4 -9
View File
@@ -348,6 +348,8 @@ static void scftorture_invoke_one(struct scf_statistics *scfp, struct torture_ra
int ret = 0;
struct scf_check *scfcp = NULL;
struct scf_selector *scfsp = scf_sel_rand(trsp);
bool is_single = (scfsp->scfs_prim == SCF_PRIM_SINGLE ||
scfsp->scfs_prim == SCF_PRIM_SINGLE_RPC);
if (scfsp->scfs_prim == SCF_PRIM_SINGLE || scfsp->scfs_wait) {
scfcp = kmalloc_obj(*scfcp, GFP_ATOMIC);
@@ -364,8 +366,6 @@ static void scftorture_invoke_one(struct scf_statistics *scfp, struct torture_ra
}
if (use_cpus_read_lock)
cpus_read_lock();
else
preempt_disable();
switch (scfsp->scfs_prim) {
case SCF_PRIM_RESCHED:
if (IS_BUILTIN(CONFIG_SCF_TORTURE_TEST)) {
@@ -411,13 +411,10 @@ static void scftorture_invoke_one(struct scf_statistics *scfp, struct torture_ra
if (!ret) {
if (use_cpus_read_lock)
cpus_read_unlock();
else
preempt_enable();
wait_for_completion(&scfcp->scfc_completion);
if (use_cpus_read_lock)
cpus_read_lock();
else
preempt_disable();
} else {
scfp->n_single_rpc_ofl++;
scf_add_to_free_list(scfcp);
@@ -452,7 +449,7 @@ static void scftorture_invoke_one(struct scf_statistics *scfp, struct torture_ra
scfcp->scfc_out = true;
}
if (scfcp && scfsp->scfs_wait) {
if (WARN_ON_ONCE((num_online_cpus() > 1 || scfsp->scfs_prim == SCF_PRIM_SINGLE) &&
if (WARN_ON_ONCE(((use_cpus_read_lock && num_online_cpus() > 1) || is_single) &&
!scfcp->scfc_out)) {
pr_warn("%s: Memory-ordering failure, scfs_prim: %d.\n", __func__, scfsp->scfs_prim);
atomic_inc(&n_mb_out_errs); // Leak rather than trash!
@@ -463,8 +460,6 @@ static void scftorture_invoke_one(struct scf_statistics *scfp, struct torture_ra
}
if (use_cpus_read_lock)
cpus_read_unlock();
else
preempt_enable();
if (allocfail)
schedule_timeout_idle((1 + longwait) * HZ); // Let no-wait handlers complete.
else if (!(torture_random(trsp) & 0xfff))