* [syzbot] [bluetooth?] possible deadlock in hci_dev_do_close
@ 2023-09-25 5:15 syzbot
2023-11-15 5:18 ` [syzbot] test syzbot
2024-02-02 20:04 ` [syzbot] Re: possible deadlock in hci_dev_do_close syzbot
0 siblings, 2 replies; 32+ messages in thread
From: syzbot @ 2023-09-25 5:15 UTC (permalink / raw)
To: arkadiusz.bokowy, johan.hedberg, linux-bluetooth, linux-kernel,
luiz.dentz, luiz.von.dentz, marcel, syzkaller-bugs
Hello,
syzbot found the following issue on:
HEAD commit: 940fcc189c51 Add linux-next specific files for 20230921
git tree: linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=127d4f64680000
kernel config: https://syzkaller.appspot.com/x/.config?x=1f140ae6e669ac24
dashboard link: https://syzkaller.appspot.com/bug?extid=4e3a76c5c505a3f49083
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1081124a680000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10cfe14a680000
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/b8921b235c24/disk-940fcc18.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c80a9f6bcdd4/vmlinux-940fcc18.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ed10a4df6950/bzImage-940fcc18.xz
The issue was bisected to:
commit 091e25d6b54992d1d702ae91cbac139d4c243251
Author: Arkadiusz Bokowy <arkadiusz.bokowy@gmail.com>
Date: Wed Sep 20 15:30:07 2023 +0000
Bluetooth: vhci: Fix race when opening vhci device
bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1326e53c680000
final oops: https://syzkaller.appspot.com/x/report.txt?x=10a6e53c680000
console output: https://syzkaller.appspot.com/x/log.txt?x=1726e53c680000
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4e3a76c5c505a3f49083@syzkaller.appspotmail.com
Fixes: 091e25d6b549 ("Bluetooth: vhci: Fix race when opening vhci device")
======================================================
WARNING: possible circular locking dependency detected
6.6.0-rc2-next-20230921-syzkaller #0 Not tainted
------------------------------------------------------
syz-executor126/5053 is trying to acquire lock:
ffff88807df1cdc0 ((work_completion)(&hdev->tx_work)){+.+.}-{0:0}, at: __flush_work+0xfa/0xa10 kernel/workqueue.c:3403
but task is already holding lock:
ffff88807df1d0b8 (&hdev->req_lock){+.+.}-{3:3}, at: hci_dev_do_close+0x26/0x90 net/bluetooth/hci_core.c:552
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #3 (&hdev->req_lock){+.+.}-{3:3}:
__mutex_lock_common kernel/locking/mutex.c:603 [inline]
__mutex_lock+0x181/0x1340 kernel/locking/mutex.c:747
hci_dev_do_close+0x26/0x90 net/bluetooth/hci_core.c:552
hci_rfkill_set_block+0x1b9/0x200 net/bluetooth/hci_core.c:956
rfkill_set_block+0x200/0x550 net/rfkill/core.c:346
rfkill_fop_write+0x2d4/0x570 net/rfkill/core.c:1306
vfs_write+0x2a4/0xe40 fs/read_write.c:582
ksys_write+0x1f0/0x250 fs/read_write.c:637
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x63/0xcd
-> #2 (rfkill_global_mutex){+.+.}-{3:3}:
__mutex_lock_common kernel/locking/mutex.c:603 [inline]
__mutex_lock+0x181/0x1340 kernel/locking/mutex.c:747
rfkill_register+0x3a/0xb30 net/rfkill/core.c:1075
hci_register_dev+0x43a/0xd40 net/bluetooth/hci_core.c:2656
__vhci_create_device+0x393/0x800 drivers/bluetooth/hci_vhci.c:437
vhci_create_device drivers/bluetooth/hci_vhci.c:478 [inline]
vhci_get_user drivers/bluetooth/hci_vhci.c:535 [inline]
vhci_write+0x2c7/0x470 drivers/bluetooth/hci_vhci.c:615
call_write_iter include/linux/fs.h:1957 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x650/0xe40 fs/read_write.c:584
ksys_write+0x12f/0x250 fs/read_write.c:637
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x63/0xcd
-> #1 (&data->open_mutex){+.+.}-{3:3}:
__mutex_lock_common kernel/locking/mutex.c:603 [inline]
__mutex_lock+0x181/0x1340 kernel/locking/mutex.c:747
vhci_send_frame+0x67/0xa0 drivers/bluetooth/hci_vhci.c:78
hci_send_frame+0x220/0x470 net/bluetooth/hci_core.c:3039
hci_sched_acl_pkt net/bluetooth/hci_core.c:3651 [inline]
hci_sched_acl net/bluetooth/hci_core.c:3736 [inline]
hci_tx_work+0x1456/0x1e40 net/bluetooth/hci_core.c:3835
process_one_work+0x884/0x15c0 kernel/workqueue.c:2630
process_scheduled_works kernel/workqueue.c:2703 [inline]
worker_thread+0x8b9/0x1290 kernel/workqueue.c:2784
kthread+0x33c/0x440 kernel/kthread.c:388
ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:304
-> #0 ((work_completion)(&hdev->tx_work)){+.+.}-{0:0}:
check_prev_add kernel/locking/lockdep.c:3134 [inline]
check_prevs_add kernel/locking/lockdep.c:3253 [inline]
validate_chain kernel/locking/lockdep.c:3868 [inline]
__lock_acquire+0x2e3d/0x5de0 kernel/locking/lockdep.c:5136
lock_acquire kernel/locking/lockdep.c:5753 [inline]
lock_acquire+0x1ae/0x510 kernel/locking/lockdep.c:5718
__flush_work+0x103/0xa10 kernel/workqueue.c:3403
hci_dev_close_sync+0x22d/0x1160 net/bluetooth/hci_sync.c:4982
hci_dev_do_close+0x2e/0x90 net/bluetooth/hci_core.c:554
hci_rfkill_set_block+0x1b9/0x200 net/bluetooth/hci_core.c:956
rfkill_set_block+0x200/0x550 net/rfkill/core.c:346
rfkill_fop_write+0x2d4/0x570 net/rfkill/core.c:1306
vfs_write+0x2a4/0xe40 fs/read_write.c:582
ksys_write+0x1f0/0x250 fs/read_write.c:637
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x63/0xcd
other info that might help us debug this:
Chain exists of:
(work_completion)(&hdev->tx_work) --> rfkill_global_mutex --> &hdev->req_lock
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&hdev->req_lock);
lock(rfkill_global_mutex);
lock(&hdev->req_lock);
lock((work_completion)(&hdev->tx_work));
*** DEADLOCK ***
2 locks held by syz-executor126/5053:
#0: ffffffff8ea842a8 (rfkill_global_mutex){+.+.}-{3:3}, at: rfkill_fop_write+0x16e/0x570 net/rfkill/core.c:1298
#1: ffff88807df1d0b8 (&hdev->req_lock){+.+.}-{3:3}, at: hci_dev_do_close+0x26/0x90 net/bluetooth/hci_core.c:552
stack backtrace:
CPU: 1 PID: 5053 Comm: syz-executor126 Not tainted 6.6.0-rc2-next-20230921-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/04/2023
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106
check_noncircular+0x311/0x3f0 kernel/locking/lockdep.c:2187
check_prev_add kernel/locking/lockdep.c:3134 [inline]
check_prevs_add kernel/locking/lockdep.c:3253 [inline]
validate_chain kernel/locking/lockdep.c:3868 [inline]
__lock_acquire+0x2e3d/0x5de0 kernel/locking/lockdep.c:5136
lock_acquire kernel/locking/lockdep.c:5753 [inline]
lock_acquire+0x1ae/0x510 kernel/locking/lockdep.c:5718
__flush_work+0x103/0xa10 kernel/workqueue.c:3403
hci_dev_close_sync+0x22d/0x1160 net/bluetooth/hci_sync.c:4982
hci_dev_do_close+0x2e/0x90 net/bluetooth/hci_core.c:554
hci_rfkill_set_block+0x1b9/0x200 net/bluetooth/hci_core.c:956
rfkill_set_block+0x200/0x550 net/rfkill/core.c:346
rfkill_fop_write+0x2d4/0x570 net/rfkill/core.c:1306
vfs_write+0x2a4/0xe40 fs/read_write.c:582
ksys_write+0x1f0/0x250 fs/read_write.c:637
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x38/0xb0 arch/x86/entry/common.c:81
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f8297388479
Code: 48 83 c4 28 c3 e8 e7 18 00 00 0f 1f 80 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffc9ef0d068 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f82973df043 RCX: 00007f8297388479
RDX: 0000000000000008 RSI: 0000000020000080 RDI: 0000000000000003
RBP: 00007ffc9ef0d0b0 R08: 000000ff00ffa650 R09: 000000ff00ffa650
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffc9ef0d098
R13: 00007f829740c5b0 R14: 0000000000000000 R15: 0000000000000001
</TASK>
---
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* Re: [syzbot] test
2022-10-21 4:45 [syzbot] UBSAN: array-index-out-of-bounds in diWrite syzbot
@ 2023-11-02 15:02 ` syzbot
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* Re: [syzbot] test
2023-09-25 5:15 [syzbot] [bluetooth?] possible deadlock in hci_dev_do_close syzbot
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Subject: test
Author: tintinm2017@gmail.com
#syz test:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
^ permalink raw reply [flat|nested] 32+ messages in thread
* [syzbot] Test
@ 2023-11-19 12:31 syzbot
0 siblings, 0 replies; 32+ messages in thread
From: syzbot @ 2023-11-19 12:31 UTC (permalink / raw)
To: linux-kernel, syzkaller-bugs
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Subject: Test
Author: tintinm2017@gmail.com
#syz test:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
^ permalink raw reply [flat|nested] 32+ messages in thread
* Re: [syzbot] Test
2023-08-19 10:47 [syzbot] [ntfs3?] WARNING in do_symlinkat (2) syzbot
@ 2023-11-28 17:38 ` syzbot
0 siblings, 0 replies; 32+ messages in thread
From: syzbot @ 2023-11-28 17:38 UTC (permalink / raw)
To: linux-kernel, syzkaller-bugs
For archival purposes, forwarding an incoming command email to
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***
Subject: Test
Author: tintinm2017@gmail.com
#syz test:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
^ permalink raw reply [flat|nested] 32+ messages in thread
* Re: [syzbot] Re: possible deadlock in hci_dev_do_close
2023-09-25 5:15 [syzbot] [bluetooth?] possible deadlock in hci_dev_do_close syzbot
2023-11-15 5:18 ` [syzbot] test syzbot
@ 2024-02-02 20:04 ` syzbot
1 sibling, 0 replies; 32+ messages in thread
From: syzbot @ 2024-02-02 20:04 UTC (permalink / raw)
To: linux-kernel
For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org.
***
Subject: Re: possible deadlock in hci_dev_do_close
Author: pchelkin@ispras.ru
#syz dup: possible deadlock in hci_rfkill_set_block
^ permalink raw reply [flat|nested] 32+ messages in thread
* Re: [syzbot] Test
2024-04-09 22:42 [syzbot] [ntfs3?] WARNING in do_open_execat (2) syzbot
@ 2024-04-15 5:22 ` syzbot
0 siblings, 0 replies; 32+ messages in thread
From: syzbot @ 2024-04-15 5:22 UTC (permalink / raw)
To: linux-kernel, syzkaller-bugs
For archival purposes, forwarding an incoming command email to
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***
Subject: Test
Author: mukattreyee@gmail.com
#syz test:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
^ permalink raw reply [flat|nested] 32+ messages in thread
* Re: [syzbot] test
2024-04-14 6:05 [syzbot] [bluetooth?] WARNING in hci_conn_set_handle syzbot
@ 2024-04-15 9:33 ` syzbot
0 siblings, 0 replies; 32+ messages in thread
From: syzbot @ 2024-04-15 9:33 UTC (permalink / raw)
To: linux-kernel, syzkaller-bugs
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Subject: test
Author: mukattreyee@gmail.com
#syz test:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
^ permalink raw reply [flat|nested] 32+ messages in thread
* Re: [syzbot] test
2024-04-15 1:54 [syzbot] [input?] WARNING in bcm5974_start_traffic/usb_submit_urb (2) syzbot
@ 2024-04-15 10:18 ` syzbot
0 siblings, 0 replies; 32+ messages in thread
From: syzbot @ 2024-04-15 10:18 UTC (permalink / raw)
To: linux-kernel, syzkaller-bugs
For archival purposes, forwarding an incoming command email to
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Subject: test
Author: mukattreyee@gmail.com
#syz test:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
^ permalink raw reply [flat|nested] 32+ messages in thread
* Re: [syzbot] Test
2024-03-29 0:16 [syzbot] [mm?] INFO: rcu detected stall in sys_clone (8) syzbot
@ 2024-05-27 12:29 ` syzbot
2024-07-03 7:26 ` syzbot
1 sibling, 0 replies; 32+ messages in thread
From: syzbot @ 2024-05-27 12:29 UTC (permalink / raw)
To: linux-kernel, syzkaller-bugs
For archival purposes, forwarding an incoming command email to
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***
Subject: Test
Author: radoslaw.zielonek@gmail.com
#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 71b1543c83d65af8215d7558d70fc2ecbee77dcf
---
net/sched/sch_taprio.c | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)
diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
index a0d54b422186..41add4a1d407 100644
--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -44,6 +44,8 @@ static struct static_key_false taprio_have_working_mqprio;
(TCA_TAPRIO_ATTR_FLAG_TXTIME_ASSIST | TCA_TAPRIO_ATTR_FLAG_FULL_OFFLOAD)
#define TAPRIO_FLAGS_INVALID U32_MAX
+#define TAPRIO_MAX_NUM_SCHEDULES_BEFORE_NOW 10
+
struct sched_entry {
/* Durations between this GCL entry and the GCL entry where the
* respective traffic class gate closes
@@ -62,6 +64,8 @@ struct sched_entry {
u32 gate_mask;
u32 interval;
u8 command;
+ /* Used to skip some cycles to prevent other tasks from starving */
+ u8 num_schedules_before_now;
};
struct sched_gate_list {
@@ -111,6 +115,9 @@ struct __tc_taprio_qopt_offload {
struct tc_taprio_qopt_offload offload;
};
+static void setup_txtime(struct taprio_sched *q,
+ struct sched_gate_list *sched, ktime_t base);
+
static void taprio_calculate_gate_durations(struct taprio_sched *q,
struct sched_gate_list *sched)
{
@@ -919,6 +926,7 @@ static enum hrtimer_restart advance_sched(struct hrtimer *timer)
struct sched_entry *entry, *next;
struct Qdisc *sch = q->root;
ktime_t end_time;
+ ktime_t basenow;
int tc;
spin_lock(&q->current_entry_lock);
@@ -977,6 +985,23 @@ static enum hrtimer_restart advance_sched(struct hrtimer *timer)
taprio_set_budgets(q, oper, next);
first_run:
+ basenow = ktime_get();
+ if (ktime_before(end_time, basenow))
+ {
+ next->num_schedules_before_now++;
+ if (next->num_schedules_before_now >= TAPRIO_MAX_NUM_SCHEDULES_BEFORE_NOW)
+ {
+ end_time = ktime_add_ns(basenow, oper->cycle_time);
+ next->end_time = end_time;
+ next->num_schedules_before_now = 0;
+ setup_txtime(q, oper, basenow);
+ }
+ }
+ else
+ {
+ next->num_schedules_before_now = 0;
+ }
+
rcu_assign_pointer(q->current_entry, next);
spin_unlock(&q->current_entry_lock);
@@ -1074,6 +1099,7 @@ static int parse_sched_entry(struct taprio_sched *q, struct nlattr *n,
}
entry->index = index;
+ entry->num_schedules_before_now = 0;
return fill_sched_entry(q, tb, entry, extack);
}
--
2.43.0
^ permalink raw reply related [flat|nested] 32+ messages in thread
* Re: [syzbot] test
2024-05-14 16:19 [syzbot] [ntfs3?] UBSAN: array-index-out-of-bounds in decompress_lznt syzbot
@ 2024-07-01 21:55 ` syzbot
0 siblings, 0 replies; 32+ messages in thread
From: syzbot @ 2024-07-01 21:55 UTC (permalink / raw)
To: linux-kernel, syzkaller-bugs
For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.
***
Subject: test
Author: mukattreyee@gmail.com
#syz test:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
^ permalink raw reply [flat|nested] 32+ messages in thread
* Re: [syzbot] Test
2024-03-29 0:16 [syzbot] [mm?] INFO: rcu detected stall in sys_clone (8) syzbot
2024-05-27 12:29 ` [syzbot] Test syzbot
@ 2024-07-03 7:26 ` syzbot
1 sibling, 0 replies; 32+ messages in thread
From: syzbot @ 2024-07-03 7:26 UTC (permalink / raw)
To: linux-kernel, syzkaller-bugs
For archival purposes, forwarding an incoming command email to
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***
Subject: Test
Author: radoslaw.zielonek@gmail.com
#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git fe46a7dd189e25604716c03576d05ac8a5209743
---
include/linux/sched.h | 7 +++++++
kernel/sched/core.c | 1 +
kernel/sched/rt.c | 26 +++++++++++++++++++++++---
kernel/signal.c | 9 +++++++++
4 files changed, 40 insertions(+), 3 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 17cb0761ff65..123bc16ad3d0 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1121,6 +1121,13 @@ struct task_struct {
size_t sas_ss_size;
unsigned int sas_ss_flags;
+ /*
+ * Number of signals received by an RT task between scheduling ticks.
+ * This counter is used to throttle RT tasks when too many signals
+ * (e.g., POSIX timers) are sent to the task, which can cause an RCU stall.
+ */
+ atomic_t rt_signals_recv_count; /* used outside of the rq lock */
+
struct callback_head *task_works;
#ifdef CONFIG_AUDIT
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d44efa0d0611..9def826bd35f 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4779,6 +4779,7 @@ int sched_fork(unsigned long clone_flags, struct task_struct *p)
p->policy = SCHED_NORMAL;
p->static_prio = NICE_TO_PRIO(0);
p->rt_priority = 0;
+ atomic_set(&p->rt_signals_recv_count, 0);
} else if (PRIO_TO_NICE(p->static_prio) < 0)
p->static_prio = NICE_TO_PRIO(0);
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 3261b067b67e..9b22d67d1746 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -24,6 +24,15 @@ int sysctl_sched_rt_period = 1000000;
*/
int sysctl_sched_rt_runtime = 950000;
+/*
+ * To avoid an RCU stall due to a large number of signals received by RT tasks
+ * (e.g., POSIX timers), the RT task needs to be throttled.
+ * When the number of signals received by an RT task during a scheduling
+ * tick period exceeds the threshold, the RT task will be throttled.
+ * The value of 100 has not been thoroughly tested and may need adjustment.
+ */
+#define RT_RECV_SGINAL_THROTTLE_THRESHOLD 100
+
#ifdef CONFIG_SYSCTL
static int sysctl_sched_rr_timeslice = (MSEC_PER_SEC * RR_TIMESLICE) / HZ;
static int sched_rt_handler(struct ctl_table *table, int write, void *buffer,
@@ -951,7 +960,7 @@ static inline int rt_se_prio(struct sched_rt_entity *rt_se)
return rt_task_of(rt_se)->prio;
}
-static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
+static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq, int rt_signal_recv)
{
u64 runtime = sched_rt_runtime(rt_rq);
@@ -966,7 +975,15 @@ static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
if (runtime == RUNTIME_INF)
return 0;
- if (rt_rq->rt_time > runtime) {
+ /*
+ * When a large number of signals are sent to this task (e.g., POSIX timers)
+ * the delta time deviates significantly from real time due to the overhead
+ * of handling signals. For RT tasks, this can cause an RCU stall.
+ * To avoid this, throttle the task when the number of signals received
+ * exceeds a certain threshold.
+ */
+ if (rt_rq->rt_time > runtime ||
+ rt_signal_recv >= RT_RECV_SGINAL_THROTTLE_THRESHOLD) {
struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
/*
@@ -1021,7 +1038,9 @@ static void update_curr_rt(struct rq *rq)
if (sched_rt_runtime(rt_rq) != RUNTIME_INF) {
raw_spin_lock(&rt_rq->rt_runtime_lock);
rt_rq->rt_time += delta_exec;
- exceeded = sched_rt_runtime_exceeded(rt_rq);
+ exceeded = sched_rt_runtime_exceeded(
+ rt_rq,
+ atomic_read(&curr->rt_signals_recv_count));
if (exceeded)
resched_curr(rq);
raw_spin_unlock(&rt_rq->rt_runtime_lock);
@@ -1029,6 +1048,7 @@ static void update_curr_rt(struct rq *rq)
do_start_rt_bandwidth(sched_rt_bandwidth(rt_rq));
}
}
+ atomic_set(&curr->rt_signals_recv_count, 0);
}
static void
diff --git a/kernel/signal.c b/kernel/signal.c
index bdca529f0f7b..d58e0ba9336c 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -629,6 +629,15 @@ int dequeue_signal(struct task_struct *tsk, sigset_t *mask,
bool resched_timer = false;
int signr;
+ /*
+ * To prevent an RCU stall due to receiving too many signals by RT tasks,
+ * count all signals regardless of their type.
+ * Based on this counter, the RT scheduler will decide whether the task
+ * should be throttled or not.
+ */
+ if (tsk->policy == SCHED_FIFO || tsk->policy == SCHED_RR)
+ atomic_inc(&tsk->rt_signals_recv_count);
+
/* We only dequeue private signals from ourselves, we don't let
* signalfd steal them
*/
--
2.43.0
^ permalink raw reply related [flat|nested] 32+ messages in thread
* Re: [syzbot] Test
2024-05-12 9:19 [syzbot] [mm?] INFO: rcu detected stall in validate_mm (3) syzbot
@ 2024-07-03 7:32 ` syzbot
2024-07-03 8:24 ` syzbot
1 sibling, 0 replies; 32+ messages in thread
From: syzbot @ 2024-07-03 7:32 UTC (permalink / raw)
To: linux-kernel, syzkaller-bugs
For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.
***
Subject: Test
Author: radoslaw.zielonek@gmail.com
#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git dccb07f2914cdab2ac3a5b6c98406f765acab803
---
include/linux/sched.h | 7 +++++++
kernel/sched/core.c | 1 +
kernel/sched/rt.c | 26 +++++++++++++++++++++++---
kernel/signal.c | 9 +++++++++
4 files changed, 40 insertions(+), 3 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 17cb0761ff65..123bc16ad3d0 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1121,6 +1121,13 @@ struct task_struct {
size_t sas_ss_size;
unsigned int sas_ss_flags;
+ /*
+ * Number of signals received by an RT task between scheduling ticks.
+ * This counter is used to throttle RT tasks when too many signals
+ * (e.g., POSIX timers) are sent to the task, which can cause an RCU stall.
+ */
+ atomic_t rt_signals_recv_count; /* used outside of the rq lock */
+
struct callback_head *task_works;
#ifdef CONFIG_AUDIT
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d44efa0d0611..9def826bd35f 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4779,6 +4779,7 @@ int sched_fork(unsigned long clone_flags, struct task_struct *p)
p->policy = SCHED_NORMAL;
p->static_prio = NICE_TO_PRIO(0);
p->rt_priority = 0;
+ atomic_set(&p->rt_signals_recv_count, 0);
} else if (PRIO_TO_NICE(p->static_prio) < 0)
p->static_prio = NICE_TO_PRIO(0);
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 3261b067b67e..9b22d67d1746 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -24,6 +24,15 @@ int sysctl_sched_rt_period = 1000000;
*/
int sysctl_sched_rt_runtime = 950000;
+/*
+ * To avoid an RCU stall due to a large number of signals received by RT tasks
+ * (e.g., POSIX timers), the RT task needs to be throttled.
+ * When the number of signals received by an RT task during a scheduling
+ * tick period exceeds the threshold, the RT task will be throttled.
+ * The value of 100 has not been thoroughly tested and may need adjustment.
+ */
+#define RT_RECV_SGINAL_THROTTLE_THRESHOLD 100
+
#ifdef CONFIG_SYSCTL
static int sysctl_sched_rr_timeslice = (MSEC_PER_SEC * RR_TIMESLICE) / HZ;
static int sched_rt_handler(struct ctl_table *table, int write, void *buffer,
@@ -951,7 +960,7 @@ static inline int rt_se_prio(struct sched_rt_entity *rt_se)
return rt_task_of(rt_se)->prio;
}
-static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
+static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq, int rt_signal_recv)
{
u64 runtime = sched_rt_runtime(rt_rq);
@@ -966,7 +975,15 @@ static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
if (runtime == RUNTIME_INF)
return 0;
- if (rt_rq->rt_time > runtime) {
+ /*
+ * When a large number of signals are sent to this task (e.g., POSIX timers)
+ * the delta time deviates significantly from real time due to the overhead
+ * of handling signals. For RT tasks, this can cause an RCU stall.
+ * To avoid this, throttle the task when the number of signals received
+ * exceeds a certain threshold.
+ */
+ if (rt_rq->rt_time > runtime ||
+ rt_signal_recv >= RT_RECV_SGINAL_THROTTLE_THRESHOLD) {
struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
/*
@@ -1021,7 +1038,9 @@ static void update_curr_rt(struct rq *rq)
if (sched_rt_runtime(rt_rq) != RUNTIME_INF) {
raw_spin_lock(&rt_rq->rt_runtime_lock);
rt_rq->rt_time += delta_exec;
- exceeded = sched_rt_runtime_exceeded(rt_rq);
+ exceeded = sched_rt_runtime_exceeded(
+ rt_rq,
+ atomic_read(&curr->rt_signals_recv_count));
if (exceeded)
resched_curr(rq);
raw_spin_unlock(&rt_rq->rt_runtime_lock);
@@ -1029,6 +1048,7 @@ static void update_curr_rt(struct rq *rq)
do_start_rt_bandwidth(sched_rt_bandwidth(rt_rq));
}
}
+ atomic_set(&curr->rt_signals_recv_count, 0);
}
static void
diff --git a/kernel/signal.c b/kernel/signal.c
index bdca529f0f7b..d58e0ba9336c 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -629,6 +629,15 @@ int dequeue_signal(struct task_struct *tsk, sigset_t *mask,
bool resched_timer = false;
int signr;
+ /*
+ * To prevent an RCU stall due to receiving too many signals by RT tasks,
+ * count all signals regardless of their type.
+ * Based on this counter, the RT scheduler will decide whether the task
+ * should be throttled or not.
+ */
+ if (tsk->policy == SCHED_FIFO || tsk->policy == SCHED_RR)
+ atomic_inc(&tsk->rt_signals_recv_count);
+
/* We only dequeue private signals from ourselves, we don't let
* signalfd steal them
*/
--
2.43.0
^ permalink raw reply related [flat|nested] 32+ messages in thread
* Re: [syzbot] Test
2024-05-12 9:19 [syzbot] [mm?] INFO: rcu detected stall in validate_mm (3) syzbot
2024-07-03 7:32 ` [syzbot] Test syzbot
@ 2024-07-03 8:24 ` syzbot
1 sibling, 0 replies; 32+ messages in thread
From: syzbot @ 2024-07-03 8:24 UTC (permalink / raw)
To: linux-kernel, syzkaller-bugs
For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.
***
Subject: Test
Author: radoslaw.zielonek@gmail.com
#syz test
---
include/linux/sched.h | 7 +++++++
kernel/sched/core.c | 1 +
kernel/sched/rt.c | 26 +++++++++++++++++++++++---
kernel/signal.c | 9 +++++++++
4 files changed, 40 insertions(+), 3 deletions(-)
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 17cb0761ff65..123bc16ad3d0 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1121,6 +1121,13 @@ struct task_struct {
size_t sas_ss_size;
unsigned int sas_ss_flags;
+ /*
+ * Number of signals received by an RT task between scheduling ticks.
+ * This counter is used to throttle RT tasks when too many signals
+ * (e.g., POSIX timers) are sent to the task, which can cause an RCU stall.
+ */
+ atomic_t rt_signals_recv_count; /* used outside of the rq lock */
+
struct callback_head *task_works;
#ifdef CONFIG_AUDIT
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d44efa0d0611..9def826bd35f 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4779,6 +4779,7 @@ int sched_fork(unsigned long clone_flags, struct task_struct *p)
p->policy = SCHED_NORMAL;
p->static_prio = NICE_TO_PRIO(0);
p->rt_priority = 0;
+ atomic_set(&p->rt_signals_recv_count, 0);
} else if (PRIO_TO_NICE(p->static_prio) < 0)
p->static_prio = NICE_TO_PRIO(0);
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 3261b067b67e..9b22d67d1746 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -24,6 +24,15 @@ int sysctl_sched_rt_period = 1000000;
*/
int sysctl_sched_rt_runtime = 950000;
+/*
+ * To avoid an RCU stall due to a large number of signals received by RT tasks
+ * (e.g., POSIX timers), the RT task needs to be throttled.
+ * When the number of signals received by an RT task during a scheduling
+ * tick period exceeds the threshold, the RT task will be throttled.
+ * The value of 100 has not been thoroughly tested and may need adjustment.
+ */
+#define RT_RECV_SGINAL_THROTTLE_THRESHOLD 100
+
#ifdef CONFIG_SYSCTL
static int sysctl_sched_rr_timeslice = (MSEC_PER_SEC * RR_TIMESLICE) / HZ;
static int sched_rt_handler(struct ctl_table *table, int write, void *buffer,
@@ -951,7 +960,7 @@ static inline int rt_se_prio(struct sched_rt_entity *rt_se)
return rt_task_of(rt_se)->prio;
}
-static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
+static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq, int rt_signal_recv)
{
u64 runtime = sched_rt_runtime(rt_rq);
@@ -966,7 +975,15 @@ static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
if (runtime == RUNTIME_INF)
return 0;
- if (rt_rq->rt_time > runtime) {
+ /*
+ * When a large number of signals are sent to this task (e.g., POSIX timers)
+ * the delta time deviates significantly from real time due to the overhead
+ * of handling signals. For RT tasks, this can cause an RCU stall.
+ * To avoid this, throttle the task when the number of signals received
+ * exceeds a certain threshold.
+ */
+ if (rt_rq->rt_time > runtime ||
+ rt_signal_recv >= RT_RECV_SGINAL_THROTTLE_THRESHOLD) {
struct rt_bandwidth *rt_b = sched_rt_bandwidth(rt_rq);
/*
@@ -1021,7 +1038,9 @@ static void update_curr_rt(struct rq *rq)
if (sched_rt_runtime(rt_rq) != RUNTIME_INF) {
raw_spin_lock(&rt_rq->rt_runtime_lock);
rt_rq->rt_time += delta_exec;
- exceeded = sched_rt_runtime_exceeded(rt_rq);
+ exceeded = sched_rt_runtime_exceeded(
+ rt_rq,
+ atomic_read(&curr->rt_signals_recv_count));
if (exceeded)
resched_curr(rq);
raw_spin_unlock(&rt_rq->rt_runtime_lock);
@@ -1029,6 +1048,7 @@ static void update_curr_rt(struct rq *rq)
do_start_rt_bandwidth(sched_rt_bandwidth(rt_rq));
}
}
+ atomic_set(&curr->rt_signals_recv_count, 0);
}
static void
diff --git a/kernel/signal.c b/kernel/signal.c
index bdca529f0f7b..d58e0ba9336c 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -629,6 +629,15 @@ int dequeue_signal(struct task_struct *tsk, sigset_t *mask,
bool resched_timer = false;
int signr;
+ /*
+ * To prevent an RCU stall due to receiving too many signals by RT tasks,
+ * count all signals regardless of their type.
+ * Based on this counter, the RT scheduler will decide whether the task
+ * should be throttled or not.
+ */
+ if (tsk->policy == SCHED_FIFO || tsk->policy == SCHED_RR)
+ atomic_inc(&tsk->rt_signals_recv_count);
+
/* We only dequeue private signals from ourselves, we don't let
* signalfd steal them
*/
--
2.43.0
^ permalink raw reply related [flat|nested] 32+ messages in thread
* Re: [syzbot] test
2024-09-23 15:46 [syzbot] [net?] possible deadlock in gtp_encap_enable_socket syzbot
@ 2024-10-01 0:57 ` syzbot
0 siblings, 0 replies; 32+ messages in thread
From: syzbot @ 2024-10-01 0:57 UTC (permalink / raw)
To: linux-kernel
For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org.
***
Subject: test
Author: danielyangkang@gmail.com
#syz test
^ permalink raw reply [flat|nested] 32+ messages in thread
* Re: [syzbot] test
2024-09-22 17:46 [syzbot] [net?] KMSAN: kernel-infoleak in move_addr_to_user (7) syzbot
@ 2024-11-03 19:27 ` syzbot
0 siblings, 0 replies; 32+ messages in thread
From: syzbot @ 2024-11-03 19:27 UTC (permalink / raw)
To: linux-kernel
For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org.
***
Subject: test
Author: danielyangkang@gmail.com
#syz test
^ permalink raw reply [flat|nested] 32+ messages in thread
end of thread, other threads:[~2024-11-03 19:27 UTC | newest]
Thread overview: 32+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2023-09-25 5:15 [syzbot] [bluetooth?] possible deadlock in hci_dev_do_close syzbot
2023-11-15 5:18 ` [syzbot] test syzbot
2024-02-02 20:04 ` [syzbot] Re: possible deadlock in hci_dev_do_close syzbot
-- strict thread matches above, loose matches on Subject: below --
2024-09-23 15:46 [syzbot] [net?] possible deadlock in gtp_encap_enable_socket syzbot
2024-10-01 0:57 ` [syzbot] test syzbot
2024-09-22 17:46 [syzbot] [net?] KMSAN: kernel-infoleak in move_addr_to_user (7) syzbot
2024-11-03 19:27 ` [syzbot] test syzbot
2024-05-14 16:19 [syzbot] [ntfs3?] UBSAN: array-index-out-of-bounds in decompress_lznt syzbot
2024-07-01 21:55 ` [syzbot] test syzbot
2024-05-12 9:19 [syzbot] [mm?] INFO: rcu detected stall in validate_mm (3) syzbot
2024-07-03 7:32 ` [syzbot] Test syzbot
2024-07-03 8:24 ` syzbot
2024-04-15 1:54 [syzbot] [input?] WARNING in bcm5974_start_traffic/usb_submit_urb (2) syzbot
2024-04-15 10:18 ` [syzbot] test syzbot
2024-04-14 6:05 [syzbot] [bluetooth?] WARNING in hci_conn_set_handle syzbot
2024-04-15 9:33 ` [syzbot] test syzbot
2024-04-09 22:42 [syzbot] [ntfs3?] WARNING in do_open_execat (2) syzbot
2024-04-15 5:22 ` [syzbot] Test syzbot
2024-03-29 0:16 [syzbot] [mm?] INFO: rcu detected stall in sys_clone (8) syzbot
2024-05-27 12:29 ` [syzbot] Test syzbot
2024-07-03 7:26 ` syzbot
2023-11-19 12:31 syzbot
2023-11-17 5:01 [syzbot] [kvm?] WARNING in kvm_mmu_notifier_invalidate_range_start (3) syzbot
2023-11-17 10:55 ` [syzbot] Test syzbot
2023-11-16 11:09 [syzbot] [kernel?] inconsistent lock state in ptrace_attach syzbot
2023-11-17 13:51 ` [syzbot] Test syzbot
2023-11-16 11:08 [syzbot] [cgroups?] possible deadlock in cgroup_free syzbot
2023-11-17 10:58 ` [syzbot] Test syzbot
2023-11-08 12:38 [syzbot] [wireless?] [net?] WARNING in ieee80211_rfkill_poll syzbot
2023-11-15 6:33 ` [syzbot] Test syzbot
2023-11-03 23:11 [syzbot] [bpf?] [net?] BUG: unable to handle kernel NULL pointer dereference in sk_psock_verdict_data_ready syzbot
2023-11-13 11:16 ` [syzbot] test syzbot
2023-10-26 18:32 [syzbot] [bpf?] [net?] BUG: unable to handle kernel NULL pointer dereference in sk_msg_recvmsg syzbot
2023-11-06 13:35 ` [syzbot] Test syzbot
2023-10-16 17:01 [syzbot] [usb?] UBSAN: array-index-out-of-bounds in usbhid_parse syzbot
2023-11-17 14:23 ` [syzbot] Test syzbot
2023-10-05 19:47 [syzbot] [ntfs3?] WARNING in attr_data_get_block (3) syzbot
2023-11-19 11:27 ` [syzbot] test syzbot
2023-09-24 7:49 [syzbot] [mm?] [hfs?] KASAN: slab-out-of-bounds Read in generic_perform_write syzbot
2023-11-17 14:24 ` [syzbot] Test syzbot
2023-09-16 1:22 [syzbot] [dri?] WARNING in drm_gem_object_handle_put_unlocked syzbot
2023-11-15 6:33 ` [syzbot] Test syzbot
2023-09-11 13:35 [syzbot] [ext4?] WARNING in ext4_discard_allocated_blocks syzbot
2023-11-17 14:17 ` [syzbot] Test syzbot
2023-08-19 10:47 [syzbot] [ntfs3?] WARNING in do_symlinkat (2) syzbot
2023-11-28 17:38 ` [syzbot] Test syzbot
2023-07-11 1:53 [syzbot] [bpf?] [reiserfs?] WARNING: locking bug in corrupted (2) syzbot
2023-11-17 14:27 ` [syzbot] Test syzbot
2022-10-21 4:45 [syzbot] UBSAN: array-index-out-of-bounds in diWrite syzbot
2023-11-02 15:02 ` [syzbot] test syzbot
2023-11-03 3:12 ` syzbot
2023-11-03 7:18 ` syzbot
2023-11-03 7:29 ` syzbot
2022-02-10 18:27 [syzbot] general protection fault in l2cap_chan_timeout (3) syzbot
2023-11-06 13:01 ` [syzbot] Test syzbot
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