* [PATCH v2] bpf: test_run: Use migrate_enable()/disable() universally
@ 2025-10-10 7:59 Sahil Chandna
2025-10-10 15:28 ` Yonghong Song
2025-10-11 13:17 ` Menglong Dong
0 siblings, 2 replies; 3+ messages in thread
From: Sahil Chandna @ 2025-10-10 7:59 UTC (permalink / raw)
To: ast, daniel, andrii, martin.lau, song, john.fastabend, haoluo,
jolsa, bpf, netdev
Cc: david.hunter.linux, skhan, khalid, chandna.linuxkernel,
syzbot+1f1fbecb9413cdbfbef8
The timer context can safely use migrate_disable()/migrate_enable()
universally instead of conditional preemption or migration disabling.
Previously, the timer was initialized in NO_PREEMPT mode by default,
which disabled preemption and forced execution in atomic context.
This caused issues on PREEMPT_RT configurations when invoking
spin_lock_bh() — a sleeping lock — leading to the following warning:
BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 6107, name: syz.0.17
preempt_count: 1, expected: 0
RCU nest depth: 1, expected: 1
Preemption disabled at:
[<ffffffff891fce58>] bpf_test_timer_enter+0xf8/0x140 net/bpf/test_run.c:42
Reported-by: syzbot+1f1fbecb9413cdbfbef8@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=1f1fbecb9413cdbfbef8
Tested-by: syzbot+1f1fbecb9413cdbfbef8@syzkaller.appspotmail.com
Signed-off-by: Sahil Chandna <chandna.linuxkernel@gmail.com>
---
Link to v1: https://lore.kernel.org/all/20251006054320.159321-1-chandna.linuxkernel@gmail.com/
Changes since v1:
- Dropped `enum { NO_PREEMPT, NO_MIGRATE } mode` from `struct bpf_test_timer`.
- Removed all conditional preempt/migrate disable logic.
- Unified timer handling to use `migrate_disable()` / `migrate_enable()` universally.
Testing:
- Reproduced syzbot bug locally using the provided reproducer.
- Observed `BUG: sleeping function called from invalid context` on v1.
- Confirmed bug disappears after applying this patch.
- Validated normal functionality of `bpf_prog_test_run_*` helpers with C
reproducer.
---
net/bpf/test_run.c | 20 ++++++--------------
1 file changed, 6 insertions(+), 14 deletions(-)
diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index dfb03ee0bb62..b23bc93e738e 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -29,7 +29,6 @@
#include <trace/events/bpf_test_run.h>
struct bpf_test_timer {
- enum { NO_PREEMPT, NO_MIGRATE } mode;
u32 i;
u64 time_start, time_spent;
};
@@ -38,10 +37,7 @@ static void bpf_test_timer_enter(struct bpf_test_timer *t)
__acquires(rcu)
{
rcu_read_lock();
- if (t->mode == NO_PREEMPT)
- preempt_disable();
- else
- migrate_disable();
+ migrate_disable();
t->time_start = ktime_get_ns();
}
@@ -50,11 +46,7 @@ static void bpf_test_timer_leave(struct bpf_test_timer *t)
__releases(rcu)
{
t->time_start = 0;
-
- if (t->mode == NO_PREEMPT)
- preempt_enable();
- else
- migrate_enable();
+ migrate_enable();
rcu_read_unlock();
}
@@ -374,7 +366,7 @@ static int bpf_test_run_xdp_live(struct bpf_prog *prog, struct xdp_buff *ctx,
{
struct xdp_test_data xdp = { .batch_size = batch_size };
- struct bpf_test_timer t = { .mode = NO_MIGRATE };
+ struct bpf_test_timer t;
int ret;
if (!repeat)
@@ -404,7 +396,7 @@ static int bpf_test_run(struct bpf_prog *prog, void *ctx, u32 repeat,
struct bpf_prog_array_item item = {.prog = prog};
struct bpf_run_ctx *old_ctx;
struct bpf_cg_run_ctx run_ctx;
- struct bpf_test_timer t = { NO_MIGRATE };
+ struct bpf_test_timer t;
enum bpf_cgroup_storage_type stype;
int ret;
@@ -1377,7 +1369,7 @@ int bpf_prog_test_run_flow_dissector(struct bpf_prog *prog,
const union bpf_attr *kattr,
union bpf_attr __user *uattr)
{
- struct bpf_test_timer t = { NO_PREEMPT };
+ struct bpf_test_timer t;
u32 size = kattr->test.data_size_in;
struct bpf_flow_dissector ctx = {};
u32 repeat = kattr->test.repeat;
@@ -1445,7 +1437,7 @@ int bpf_prog_test_run_flow_dissector(struct bpf_prog *prog,
int bpf_prog_test_run_sk_lookup(struct bpf_prog *prog, const union bpf_attr *kattr,
union bpf_attr __user *uattr)
{
- struct bpf_test_timer t = { NO_PREEMPT };
+ struct bpf_test_timer t;
struct bpf_prog_array *progs = NULL;
struct bpf_sk_lookup_kern ctx = {};
u32 repeat = kattr->test.repeat;
--
2.50.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v2] bpf: test_run: Use migrate_enable()/disable() universally
2025-10-10 7:59 [PATCH v2] bpf: test_run: Use migrate_enable()/disable() universally Sahil Chandna
@ 2025-10-10 15:28 ` Yonghong Song
2025-10-11 13:17 ` Menglong Dong
1 sibling, 0 replies; 3+ messages in thread
From: Yonghong Song @ 2025-10-10 15:28 UTC (permalink / raw)
To: Sahil Chandna, ast, daniel, andrii, martin.lau, song,
john.fastabend, haoluo, jolsa, bpf, netdev
Cc: david.hunter.linux, skhan, khalid, syzbot+1f1fbecb9413cdbfbef8
On 10/10/25 12:59 AM, Sahil Chandna wrote:
> The timer context can safely use migrate_disable()/migrate_enable()
> universally instead of conditional preemption or migration disabling.
> Previously, the timer was initialized in NO_PREEMPT mode by default,
> which disabled preemption and forced execution in atomic context.
> This caused issues on PREEMPT_RT configurations when invoking
> spin_lock_bh() — a sleeping lock — leading to the following warning:
>
> BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48
> in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 6107, name: syz.0.17
> preempt_count: 1, expected: 0
> RCU nest depth: 1, expected: 1
> Preemption disabled at:
> [<ffffffff891fce58>] bpf_test_timer_enter+0xf8/0x140 net/bpf/test_run.c:42
>
> Reported-by: syzbot+1f1fbecb9413cdbfbef8@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=1f1fbecb9413cdbfbef8
> Tested-by: syzbot+1f1fbecb9413cdbfbef8@syzkaller.appspotmail.com
> Signed-off-by: Sahil Chandna <chandna.linuxkernel@gmail.com>
>
> ---
> Link to v1: https://lore.kernel.org/all/20251006054320.159321-1-chandna.linuxkernel@gmail.com/
>
> Changes since v1:
> - Dropped `enum { NO_PREEMPT, NO_MIGRATE } mode` from `struct bpf_test_timer`.
> - Removed all conditional preempt/migrate disable logic.
> - Unified timer handling to use `migrate_disable()` / `migrate_enable()` universally.
>
> Testing:
> - Reproduced syzbot bug locally using the provided reproducer.
> - Observed `BUG: sleeping function called from invalid context` on v1.
> - Confirmed bug disappears after applying this patch.
> - Validated normal functionality of `bpf_prog_test_run_*` helpers with C
> reproducer.
> ---
> net/bpf/test_run.c | 20 ++++++--------------
> 1 file changed, 6 insertions(+), 14 deletions(-)
>
> diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
> index dfb03ee0bb62..b23bc93e738e 100644
> --- a/net/bpf/test_run.c
> +++ b/net/bpf/test_run.c
> @@ -29,7 +29,6 @@
> #include <trace/events/bpf_test_run.h>
>
> struct bpf_test_timer {
> - enum { NO_PREEMPT, NO_MIGRATE } mode;
> u32 i;
> u64 time_start, time_spent;
> };
> @@ -38,10 +37,7 @@ static void bpf_test_timer_enter(struct bpf_test_timer *t)
> __acquires(rcu)
> {
> rcu_read_lock();
> - if (t->mode == NO_PREEMPT)
> - preempt_disable();
> - else
> - migrate_disable();
> + migrate_disable();
>
> t->time_start = ktime_get_ns();
> }
> @@ -50,11 +46,7 @@ static void bpf_test_timer_leave(struct bpf_test_timer *t)
> __releases(rcu)
> {
> t->time_start = 0;
> -
> - if (t->mode == NO_PREEMPT)
> - preempt_enable();
> - else
> - migrate_enable();
> + migrate_enable();
> rcu_read_unlock();
> }
>
> @@ -374,7 +366,7 @@ static int bpf_test_run_xdp_live(struct bpf_prog *prog, struct xdp_buff *ctx,
>
> {
> struct xdp_test_data xdp = { .batch_size = batch_size };
> - struct bpf_test_timer t = { .mode = NO_MIGRATE };
> + struct bpf_test_timer t;
We still need to initialize 'struct bpf_test_timer t' with t.time_spent = 0 like
struct bpf_test_timer t = {};
since time_spent is used like
t->time_spent += ktime_get_ns() - t->time_start;
> int ret;
>
> if (!repeat)
> @@ -404,7 +396,7 @@ static int bpf_test_run(struct bpf_prog *prog, void *ctx, u32 repeat,
> struct bpf_prog_array_item item = {.prog = prog};
> struct bpf_run_ctx *old_ctx;
> struct bpf_cg_run_ctx run_ctx;
> - struct bpf_test_timer t = { NO_MIGRATE };
> + struct bpf_test_timer t;
> enum bpf_cgroup_storage_type stype;
> int ret;
>
> @@ -1377,7 +1369,7 @@ int bpf_prog_test_run_flow_dissector(struct bpf_prog *prog,
> const union bpf_attr *kattr,
> union bpf_attr __user *uattr)
> {
> - struct bpf_test_timer t = { NO_PREEMPT };
> + struct bpf_test_timer t;
> u32 size = kattr->test.data_size_in;
> struct bpf_flow_dissector ctx = {};
> u32 repeat = kattr->test.repeat;
> @@ -1445,7 +1437,7 @@ int bpf_prog_test_run_flow_dissector(struct bpf_prog *prog,
> int bpf_prog_test_run_sk_lookup(struct bpf_prog *prog, const union bpf_attr *kattr,
> union bpf_attr __user *uattr)
> {
> - struct bpf_test_timer t = { NO_PREEMPT };
> + struct bpf_test_timer t;
> struct bpf_prog_array *progs = NULL;
> struct bpf_sk_lookup_kern ctx = {};
> u32 repeat = kattr->test.repeat;
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v2] bpf: test_run: Use migrate_enable()/disable() universally
2025-10-10 7:59 [PATCH v2] bpf: test_run: Use migrate_enable()/disable() universally Sahil Chandna
2025-10-10 15:28 ` Yonghong Song
@ 2025-10-11 13:17 ` Menglong Dong
1 sibling, 0 replies; 3+ messages in thread
From: Menglong Dong @ 2025-10-11 13:17 UTC (permalink / raw)
To: Sahil Chandna
Cc: ast, daniel, andrii, martin.lau, song, john.fastabend, haoluo,
jolsa, bpf, netdev, david.hunter.linux, skhan, khalid,
chandna.linuxkernel, syzbot+1f1fbecb9413cdbfbef8
On 2025/10/10 15:59, Sahil Chandna wrote:
> The timer context can safely use migrate_disable()/migrate_enable()
> universally instead of conditional preemption or migration disabling.
> Previously, the timer was initialized in NO_PREEMPT mode by default,
> which disabled preemption and forced execution in atomic context.
> This caused issues on PREEMPT_RT configurations when invoking
> spin_lock_bh() — a sleeping lock — leading to the following warning:
>
> BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48
> in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 6107, name: syz.0.17
> preempt_count: 1, expected: 0
> RCU nest depth: 1, expected: 1
> Preemption disabled at:
> [<ffffffff891fce58>] bpf_test_timer_enter+0xf8/0x140 net/bpf/test_run.c:42
>
> Reported-by: syzbot+1f1fbecb9413cdbfbef8@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=1f1fbecb9413cdbfbef8
> Tested-by: syzbot+1f1fbecb9413cdbfbef8@syzkaller.appspotmail.com
> Signed-off-by: Sahil Chandna <chandna.linuxkernel@gmail.com>
>
> ---
> Link to v1: https://lore.kernel.org/all/20251006054320.159321-1-chandna.linuxkernel@gmail.com/
>
> Changes since v1:
> - Dropped `enum { NO_PREEMPT, NO_MIGRATE } mode` from `struct bpf_test_timer`.
> - Removed all conditional preempt/migrate disable logic.
> - Unified timer handling to use `migrate_disable()` / `migrate_enable()` universally.
>
> Testing:
> - Reproduced syzbot bug locally using the provided reproducer.
> - Observed `BUG: sleeping function called from invalid context` on v1.
> - Confirmed bug disappears after applying this patch.
> - Validated normal functionality of `bpf_prog_test_run_*` helpers with C
> reproducer.
> ---
> net/bpf/test_run.c | 20 ++++++--------------
> 1 file changed, 6 insertions(+), 14 deletions(-)
>
> diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
> index dfb03ee0bb62..b23bc93e738e 100644
> --- a/net/bpf/test_run.c
> +++ b/net/bpf/test_run.c
> @@ -29,7 +29,6 @@
> #include <trace/events/bpf_test_run.h>
>
> struct bpf_test_timer {
> - enum { NO_PREEMPT, NO_MIGRATE } mode;
> u32 i;
> u64 time_start, time_spent;
> };
> @@ -38,10 +37,7 @@ static void bpf_test_timer_enter(struct bpf_test_timer *t)
> __acquires(rcu)
> {
> rcu_read_lock();
> - if (t->mode == NO_PREEMPT)
> - preempt_disable();
> - else
> - migrate_disable();
> + migrate_disable();
Maybe we can use rcu_read_lock_dont_migrate/rcu_read_unlock_migrate
here instead, which has better performance :)
Thanks!
Menglong Dong
>
> t->time_start = ktime_get_ns();
> }
> @@ -50,11 +46,7 @@ static void bpf_test_timer_leave(struct bpf_test_timer *t)
> __releases(rcu)
> {
> t->time_start = 0;
> -
> - if (t->mode == NO_PREEMPT)
> - preempt_enable();
> - else
> - migrate_enable();
> + migrate_enable();
> rcu_read_unlock();
> }
>
> @@ -374,7 +366,7 @@ static int bpf_test_run_xdp_live(struct bpf_prog *prog, struct xdp_buff *ctx,
>
> {
> struct xdp_test_data xdp = { .batch_size = batch_size };
> - struct bpf_test_timer t = { .mode = NO_MIGRATE };
> + struct bpf_test_timer t;
> int ret;
>
> if (!repeat)
> @@ -404,7 +396,7 @@ static int bpf_test_run(struct bpf_prog *prog, void *ctx, u32 repeat,
> struct bpf_prog_array_item item = {.prog = prog};
> struct bpf_run_ctx *old_ctx;
> struct bpf_cg_run_ctx run_ctx;
> - struct bpf_test_timer t = { NO_MIGRATE };
> + struct bpf_test_timer t;
> enum bpf_cgroup_storage_type stype;
> int ret;
>
> @@ -1377,7 +1369,7 @@ int bpf_prog_test_run_flow_dissector(struct bpf_prog *prog,
> const union bpf_attr *kattr,
> union bpf_attr __user *uattr)
> {
> - struct bpf_test_timer t = { NO_PREEMPT };
> + struct bpf_test_timer t;
> u32 size = kattr->test.data_size_in;
> struct bpf_flow_dissector ctx = {};
> u32 repeat = kattr->test.repeat;
> @@ -1445,7 +1437,7 @@ int bpf_prog_test_run_flow_dissector(struct bpf_prog *prog,
> int bpf_prog_test_run_sk_lookup(struct bpf_prog *prog, const union bpf_attr *kattr,
> union bpf_attr __user *uattr)
> {
> - struct bpf_test_timer t = { NO_PREEMPT };
> + struct bpf_test_timer t;
> struct bpf_prog_array *progs = NULL;
> struct bpf_sk_lookup_kern ctx = {};
> u32 repeat = kattr->test.repeat;
>
^ permalink raw reply [flat|nested] 3+ messages in thread
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2025-10-10 7:59 [PATCH v2] bpf: test_run: Use migrate_enable()/disable() universally Sahil Chandna
2025-10-10 15:28 ` Yonghong Song
2025-10-11 13:17 ` Menglong Dong
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