* [PATCH] arm64: Use a raw spinlock in __install_bp_hardening_cb()
@ 2018-11-27 15:35 James Morse
2018-11-27 19:15 ` Will Deacon
2018-11-28 7:51 ` Marc Zyngier
0 siblings, 2 replies; 3+ messages in thread
From: James Morse @ 2018-11-27 15:35 UTC (permalink / raw)
To: linux-arm-kernel
__install_bp_hardening_cb() is called via stop_machine() as part
of the cpu_enable callback. To force each CPU to take its turn
when allocating slots, they take a spinlock.
With the RT patches applied, the spinlock becomes a mutex,
and we get warnings about sleeping while in stop_machine():
| [ 0.319176] CPU features: detected: RAS Extension Support
| [ 0.319950] BUG: scheduling while atomic: migration/3/36/0x00000002
| [ 0.319955] Modules linked in:
| [ 0.319958] Preemption disabled at:
| [ 0.319969] [<ffff000008181ae4>] cpu_stopper_thread+0x7c/0x108
| [ 0.319973] CPU: 3 PID: 36 Comm: migration/3 Not tainted 4.19.1-rt3-00250-g330fc2c2a880 #2
| [ 0.319975] Hardware name: linux,dummy-virt (DT)
| [ 0.319976] Call trace:
| [ 0.319981] dump_backtrace+0x0/0x148
| [ 0.319983] show_stack+0x14/0x20
| [ 0.319987] dump_stack+0x80/0xa4
| [ 0.319989] __schedule_bug+0x94/0xb0
| [ 0.319991] __schedule+0x510/0x560
| [ 0.319992] schedule+0x38/0xe8
| [ 0.319994] rt_spin_lock_slowlock_locked+0xf0/0x278
| [ 0.319996] rt_spin_lock_slowlock+0x5c/0x90
| [ 0.319998] rt_spin_lock+0x54/0x58
| [ 0.320000] enable_smccc_arch_workaround_1+0xdc/0x260
| [ 0.320001] __enable_cpu_capability+0x10/0x20
| [ 0.320003] multi_cpu_stop+0x84/0x108
| [ 0.320004] cpu_stopper_thread+0x84/0x108
| [ 0.320008] smpboot_thread_fn+0x1e8/0x2b0
| [ 0.320009] kthread+0x124/0x128
| [ 0.320010] ret_from_fork+0x10/0x18
Switch this to a raw spinlock, as we know this is only called with
IRQs masked.
Signed-off-by: James Morse <james.morse@arm.com>
---
arch/arm64/kernel/cpu_errata.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index a509e35132d2..00d93a91c4d5 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -135,7 +135,7 @@ static void __install_bp_hardening_cb(bp_hardening_cb_t fn,
const char *hyp_vecs_start,
const char *hyp_vecs_end)
{
- static DEFINE_SPINLOCK(bp_lock);
+ static DEFINE_RAW_SPINLOCK(bp_lock);
int cpu, slot = -1;
/*
@@ -147,7 +147,7 @@ static void __install_bp_hardening_cb(bp_hardening_cb_t fn,
return;
}
- spin_lock(&bp_lock);
+ raw_spin_lock(&bp_lock);
for_each_possible_cpu(cpu) {
if (per_cpu(bp_hardening_data.fn, cpu) == fn) {
slot = per_cpu(bp_hardening_data.hyp_vectors_slot, cpu);
@@ -163,7 +163,7 @@ static void __install_bp_hardening_cb(bp_hardening_cb_t fn,
__this_cpu_write(bp_hardening_data.hyp_vectors_slot, slot);
__this_cpu_write(bp_hardening_data.fn, fn);
- spin_unlock(&bp_lock);
+ raw_spin_unlock(&bp_lock);
}
#else
#define __smccc_workaround_1_smc_start NULL
--
2.19.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* [PATCH] arm64: Use a raw spinlock in __install_bp_hardening_cb()
2018-11-27 15:35 [PATCH] arm64: Use a raw spinlock in __install_bp_hardening_cb() James Morse
@ 2018-11-27 19:15 ` Will Deacon
2018-11-28 7:51 ` Marc Zyngier
1 sibling, 0 replies; 3+ messages in thread
From: Will Deacon @ 2018-11-27 19:15 UTC (permalink / raw)
To: linux-arm-kernel
On Tue, Nov 27, 2018 at 03:35:21PM +0000, James Morse wrote:
> __install_bp_hardening_cb() is called via stop_machine() as part
> of the cpu_enable callback. To force each CPU to take its turn
> when allocating slots, they take a spinlock.
>
> With the RT patches applied, the spinlock becomes a mutex,
> and we get warnings about sleeping while in stop_machine():
> | [ 0.319176] CPU features: detected: RAS Extension Support
> | [ 0.319950] BUG: scheduling while atomic: migration/3/36/0x00000002
> | [ 0.319955] Modules linked in:
> | [ 0.319958] Preemption disabled at:
> | [ 0.319969] [<ffff000008181ae4>] cpu_stopper_thread+0x7c/0x108
> | [ 0.319973] CPU: 3 PID: 36 Comm: migration/3 Not tainted 4.19.1-rt3-00250-g330fc2c2a880 #2
> | [ 0.319975] Hardware name: linux,dummy-virt (DT)
> | [ 0.319976] Call trace:
> | [ 0.319981] dump_backtrace+0x0/0x148
> | [ 0.319983] show_stack+0x14/0x20
> | [ 0.319987] dump_stack+0x80/0xa4
> | [ 0.319989] __schedule_bug+0x94/0xb0
> | [ 0.319991] __schedule+0x510/0x560
> | [ 0.319992] schedule+0x38/0xe8
> | [ 0.319994] rt_spin_lock_slowlock_locked+0xf0/0x278
> | [ 0.319996] rt_spin_lock_slowlock+0x5c/0x90
> | [ 0.319998] rt_spin_lock+0x54/0x58
> | [ 0.320000] enable_smccc_arch_workaround_1+0xdc/0x260
> | [ 0.320001] __enable_cpu_capability+0x10/0x20
> | [ 0.320003] multi_cpu_stop+0x84/0x108
> | [ 0.320004] cpu_stopper_thread+0x84/0x108
> | [ 0.320008] smpboot_thread_fn+0x1e8/0x2b0
> | [ 0.320009] kthread+0x124/0x128
> | [ 0.320010] ret_from_fork+0x10/0x18
>
> Switch this to a raw spinlock, as we know this is only called with
> IRQs masked.
There might be a lock-free way to do this, but this isn't a fast-path
so I've queued up your patch for 4.21.
Thanks!
Will
^ permalink raw reply [flat|nested] 3+ messages in thread
* [PATCH] arm64: Use a raw spinlock in __install_bp_hardening_cb()
2018-11-27 15:35 [PATCH] arm64: Use a raw spinlock in __install_bp_hardening_cb() James Morse
2018-11-27 19:15 ` Will Deacon
@ 2018-11-28 7:51 ` Marc Zyngier
1 sibling, 0 replies; 3+ messages in thread
From: Marc Zyngier @ 2018-11-28 7:51 UTC (permalink / raw)
To: linux-arm-kernel
On Tue, 27 Nov 2018 15:35:21 +0000,
James Morse <james.morse@arm.com> wrote:
>
> __install_bp_hardening_cb() is called via stop_machine() as part
> of the cpu_enable callback. To force each CPU to take its turn
> when allocating slots, they take a spinlock.
>
> With the RT patches applied, the spinlock becomes a mutex,
> and we get warnings about sleeping while in stop_machine():
> | [ 0.319176] CPU features: detected: RAS Extension Support
> | [ 0.319950] BUG: scheduling while atomic: migration/3/36/0x00000002
> | [ 0.319955] Modules linked in:
> | [ 0.319958] Preemption disabled at:
> | [ 0.319969] [<ffff000008181ae4>] cpu_stopper_thread+0x7c/0x108
> | [ 0.319973] CPU: 3 PID: 36 Comm: migration/3 Not tainted 4.19.1-rt3-00250-g330fc2c2a880 #2
> | [ 0.319975] Hardware name: linux,dummy-virt (DT)
> | [ 0.319976] Call trace:
> | [ 0.319981] dump_backtrace+0x0/0x148
> | [ 0.319983] show_stack+0x14/0x20
> | [ 0.319987] dump_stack+0x80/0xa4
> | [ 0.319989] __schedule_bug+0x94/0xb0
> | [ 0.319991] __schedule+0x510/0x560
> | [ 0.319992] schedule+0x38/0xe8
> | [ 0.319994] rt_spin_lock_slowlock_locked+0xf0/0x278
> | [ 0.319996] rt_spin_lock_slowlock+0x5c/0x90
> | [ 0.319998] rt_spin_lock+0x54/0x58
> | [ 0.320000] enable_smccc_arch_workaround_1+0xdc/0x260
> | [ 0.320001] __enable_cpu_capability+0x10/0x20
> | [ 0.320003] multi_cpu_stop+0x84/0x108
> | [ 0.320004] cpu_stopper_thread+0x84/0x108
> | [ 0.320008] smpboot_thread_fn+0x1e8/0x2b0
> | [ 0.320009] kthread+0x124/0x128
> | [ 0.320010] ret_from_fork+0x10/0x18
>
> Switch this to a raw spinlock, as we know this is only called with
> IRQs masked.
>
> Signed-off-by: James Morse <james.morse@arm.com>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
M.
--
Jazz is not dead, it just smell funny.
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2018-11-28 7:51 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2018-11-27 15:35 [PATCH] arm64: Use a raw spinlock in __install_bp_hardening_cb() James Morse
2018-11-27 19:15 ` Will Deacon
2018-11-28 7:51 ` Marc Zyngier
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).