On an Ampere Altra,
Running a preemp_rt kernel based on v5.19-rc3-rt5 on an
Ampere Altra triggers:
[ 15.683141] BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:46
[ 15.683154] in_atomic(): 0, irqs_disabled(): 128, non_block: 0, pid: 24, name: cpuhp/0
[ 15.683157] preempt_count: 0, expected: 0
[ 15.683159] RCU nest depth: 0, expected: 0
[ 15.683163] 3 locks held by cpuhp/0/24:
[ 15.683167] #0: ffffda30217c70d0 (cpu_hotplug_lock){++++}-{0:0}, at: cpuhp_thread_fun+0x5c/0x248
[ 15.683201] #1: ffffda30217c7120 (cpuhp_state-up){+.+.}-{0:0}, at: cpuhp_thread_fun+0x5c/0x248
[ 15.683205] #2: ffffda3021c711f0 (sdei_list_lock){....}-{3:3}, at: sdei_cpuhp_up+0x3c/0x130
[ 15.683224] irq event stamp: 36
[ 15.683226] hardirqs last enabled at (35): [<ffffda301e85b7bc>] finish_task_switch+0xb4/0x2b0
[ 15.683236] hardirqs last disabled at (36): [<ffffda301e812fec>] cpuhp_thread_fun+0x21c/0x248
[ 15.683238] softirqs last enabled at (0): [<ffffda301e80b184>] copy_process+0x63c/0x1ac0
[ 15.683245] softirqs last disabled at (0): [<0000000000000000>] 0x0
[ 15.683258] CPU: 0 PID: 24 Comm: cpuhp/0 Not tainted 5.19.0-rc3-rt5-[...]
[ 15.683265] Hardware name: WIWYNN Mt.Jade Server System B81.03001.0005/Mt.Jade Motherboard, BIOS 1.08.20220218 (SCP: 1.08.20220218) 2022/02/18
[ 15.683268] Call trace:
[ 15.683271] dump_backtrace+0x114/0x120
[ 15.683277] show_stack+0x20/0x70
[ 15.683279] dump_stack_lvl+0x9c/0xd8
[ 15.683288] dump_stack+0x18/0x34
[ 15.683289] __might_resched+0x188/0x228
[ 15.683292] rt_spin_lock+0x70/0x120
[ 15.683301] sdei_cpuhp_up+0x3c/0x130
[ 15.683303] cpuhp_invoke_callback+0x250/0xf08
[ 15.683305] cpuhp_thread_fun+0x120/0x248
[ 15.683308] smpboot_thread_fn+0x280/0x320
[ 15.683315] kthread+0x130/0x140
[ 15.683321] ret_from_fork+0x10/0x20
sdei_cpuhp_up() is called in the STARTING hotplug section,
which runs whith interrupts disabled. Move CPUHP_AP_ARM_SDEI_
state to the _ONLINE section to execute the cpuhp cb with
preemption enabled.
Some SDEI calls (e.g. SDEI_1_0_FN_SDEI_PE_MASK) take actions on the
calling CPU. It is checked that preemption is disabled for them.
_ONLINE cpuhp cb are executed in the 'per CPU hotplug thread'.
Preemption is enabled in those threads, but their cpumask is limited
to 1 CPU.
Move 'WARN_ON_ONCE(preemptible())' statements so that SDEI cpuhp cb
don't trigger them. This means that no check will be done for some
cases, e.g. sdei_mask_local_cpu() invocations.
Also add a check for the SDEI_1_0_FN_SDEI_PRIVATE_RESET SDEI call
which acts on the calling CPU.
Suggested-by: James Morse <[email protected]>
Signed-off-by: Pierre Gondois <[email protected]>
---
drivers/firmware/arm_sdei.c | 28 ++++++++++++++--------------
include/linux/cpuhotplug.h | 2 +-
2 files changed, 15 insertions(+), 15 deletions(-)
diff --git a/drivers/firmware/arm_sdei.c b/drivers/firmware/arm_sdei.c
index 1e1a51510e83..9b03e164a37a 100644
--- a/drivers/firmware/arm_sdei.c
+++ b/drivers/firmware/arm_sdei.c
@@ -301,8 +301,6 @@ int sdei_mask_local_cpu(void)
{
int err;
- WARN_ON_ONCE(preemptible());
-
err = invoke_sdei_fn(SDEI_1_0_FN_SDEI_PE_MASK, 0, 0, 0, 0, 0, NULL);
if (err && err != -EIO) {
pr_warn_once("failed to mask CPU[%u]: %d\n",
@@ -315,6 +313,7 @@ int sdei_mask_local_cpu(void)
static void _ipi_mask_cpu(void *ignored)
{
+ WARN_ON_ONCE(preemptible());
sdei_mask_local_cpu();
}
@@ -322,8 +321,6 @@ int sdei_unmask_local_cpu(void)
{
int err;
- WARN_ON_ONCE(preemptible());
-
err = invoke_sdei_fn(SDEI_1_0_FN_SDEI_PE_UNMASK, 0, 0, 0, 0, 0, NULL);
if (err && err != -EIO) {
pr_warn_once("failed to unmask CPU[%u]: %d\n",
@@ -336,6 +333,7 @@ int sdei_unmask_local_cpu(void)
static void _ipi_unmask_cpu(void *ignored)
{
+ WARN_ON_ONCE(preemptible());
sdei_unmask_local_cpu();
}
@@ -343,6 +341,8 @@ static void _ipi_private_reset(void *ignored)
{
int err;
+ WARN_ON_ONCE(preemptible());
+
err = invoke_sdei_fn(SDEI_1_0_FN_SDEI_PRIVATE_RESET, 0, 0, 0, 0, 0,
NULL);
if (err && err != -EIO)
@@ -389,8 +389,6 @@ static void _local_event_enable(void *data)
int err;
struct sdei_crosscall_args *arg = data;
- WARN_ON_ONCE(preemptible());
-
err = sdei_api_event_enable(arg->event->event_num);
sdei_cross_call_return(arg, err);
@@ -401,6 +399,8 @@ int sdei_event_enable(u32 event_num)
int err = -EINVAL;
struct sdei_event *event;
+ WARN_ON_ONCE(preemptible());
+
mutex_lock(&sdei_events_lock);
event = sdei_event_find(event_num);
if (!event) {
@@ -479,8 +479,6 @@ static void _local_event_unregister(void *data)
int err;
struct sdei_crosscall_args *arg = data;
- WARN_ON_ONCE(preemptible());
-
err = sdei_api_event_unregister(arg->event->event_num);
sdei_cross_call_return(arg, err);
@@ -492,6 +490,7 @@ int sdei_event_unregister(u32 event_num)
struct sdei_event *event;
WARN_ON(in_nmi());
+ WARN_ON_ONCE(preemptible());
mutex_lock(&sdei_events_lock);
event = sdei_event_find(event_num);
@@ -561,8 +560,6 @@ static void _local_event_register(void *data)
struct sdei_registered_event *reg;
struct sdei_crosscall_args *arg = data;
- WARN_ON(preemptible());
-
reg = per_cpu_ptr(arg->event->private_registered, smp_processor_id());
err = sdei_api_event_register(arg->event->event_num, sdei_entry_point,
reg, 0, 0);
@@ -576,6 +573,7 @@ int sdei_event_register(u32 event_num, sdei_event_callback *cb, void *arg)
struct sdei_event *event;
WARN_ON(in_nmi());
+ WARN_ON_ONCE(preemptible());
mutex_lock(&sdei_events_lock);
if (sdei_event_find(event_num)) {
@@ -717,6 +715,8 @@ static int sdei_pm_notifier(struct notifier_block *nb, unsigned long action,
{
int rv;
+ WARN_ON_ONCE(preemptible());
+
switch (action) {
case CPU_PM_ENTER:
rv = sdei_mask_local_cpu();
@@ -765,7 +765,7 @@ static int sdei_device_freeze(struct device *dev)
int err;
/* unregister private events */
- cpuhp_remove_state(CPUHP_AP_ARM_SDEI_STARTING);
+ cpuhp_remove_state(CPUHP_AP_ARM_SDEI_ONLINE);
err = sdei_unregister_shared();
if (err)
@@ -786,7 +786,7 @@ static int sdei_device_thaw(struct device *dev)
return err;
}
- err = cpuhp_setup_state(CPUHP_AP_ARM_SDEI_STARTING, "SDEI",
+ err = cpuhp_setup_state(CPUHP_AP_ARM_SDEI_ONLINE, "SDEI",
&sdei_cpuhp_up, &sdei_cpuhp_down);
if (err)
pr_warn("Failed to re-register CPU hotplug notifier...\n");
@@ -823,7 +823,7 @@ static int sdei_reboot_notifier(struct notifier_block *nb, unsigned long action,
* We are going to reset the interface, after this there is no point
* doing work when we take CPUs offline.
*/
- cpuhp_remove_state(CPUHP_AP_ARM_SDEI_STARTING);
+ cpuhp_remove_state(CPUHP_AP_ARM_SDEI_ONLINE);
sdei_platform_reset();
@@ -1003,7 +1003,7 @@ static int sdei_probe(struct platform_device *pdev)
goto remove_cpupm;
}
- err = cpuhp_setup_state(CPUHP_AP_ARM_SDEI_STARTING, "SDEI",
+ err = cpuhp_setup_state(CPUHP_AP_ARM_SDEI_ONLINE, "SDEI",
&sdei_cpuhp_up, &sdei_cpuhp_down);
if (err) {
pr_warn("Failed to register CPU hotplug notifier...\n");
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index f61447913db9..63b89e00a4c3 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -161,7 +161,6 @@ enum cpuhp_state {
CPUHP_AP_PERF_X86_CSTATE_STARTING,
CPUHP_AP_PERF_XTENSA_STARTING,
CPUHP_AP_MIPS_OP_LOONGSON3_STARTING,
- CPUHP_AP_ARM_SDEI_STARTING,
CPUHP_AP_ARM_VFP_STARTING,
CPUHP_AP_ARM64_DEBUG_MONITORS_STARTING,
CPUHP_AP_PERF_ARM_HW_BREAKPOINT_STARTING,
@@ -209,6 +208,7 @@ enum cpuhp_state {
CPUHP_AP_IRQ_AFFINITY_ONLINE,
CPUHP_AP_BLK_MQ_ONLINE,
CPUHP_AP_ARM_MVEBU_SYNC_CLOCKS,
+ CPUHP_AP_ARM_SDEI_ONLINE,
CPUHP_AP_X86_INTEL_EPB_ONLINE,
CPUHP_AP_PERF_ONLINE,
CPUHP_AP_PERF_X86_ONLINE,
--
2.25.1
On Tue, Oct 18, 2022 at 03:04:53PM +0200, Pierre Gondois wrote:
> On an Ampere Altra,
> Running a preemp_rt kernel based on v5.19-rc3-rt5 on an
> Ampere Altra triggers:
> [ 15.683141] BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:46
> [ 15.683154] in_atomic(): 0, irqs_disabled(): 128, non_block: 0, pid: 24, name: cpuhp/0
> [ 15.683157] preempt_count: 0, expected: 0
> [ 15.683159] RCU nest depth: 0, expected: 0
> [ 15.683163] 3 locks held by cpuhp/0/24:
> [ 15.683167] #0: ffffda30217c70d0 (cpu_hotplug_lock){++++}-{0:0}, at: cpuhp_thread_fun+0x5c/0x248
> [ 15.683201] #1: ffffda30217c7120 (cpuhp_state-up){+.+.}-{0:0}, at: cpuhp_thread_fun+0x5c/0x248
> [ 15.683205] #2: ffffda3021c711f0 (sdei_list_lock){....}-{3:3}, at: sdei_cpuhp_up+0x3c/0x130
> [ 15.683224] irq event stamp: 36
> [ 15.683226] hardirqs last enabled at (35): [<ffffda301e85b7bc>] finish_task_switch+0xb4/0x2b0
> [ 15.683236] hardirqs last disabled at (36): [<ffffda301e812fec>] cpuhp_thread_fun+0x21c/0x248
> [ 15.683238] softirqs last enabled at (0): [<ffffda301e80b184>] copy_process+0x63c/0x1ac0
> [ 15.683245] softirqs last disabled at (0): [<0000000000000000>] 0x0
> [ 15.683258] CPU: 0 PID: 24 Comm: cpuhp/0 Not tainted 5.19.0-rc3-rt5-[...]
> [ 15.683265] Hardware name: WIWYNN Mt.Jade Server System B81.03001.0005/Mt.Jade Motherboard, BIOS 1.08.20220218 (SCP: 1.08.20220218) 2022/02/18
> [ 15.683268] Call trace:
> [ 15.683271] dump_backtrace+0x114/0x120
> [ 15.683277] show_stack+0x20/0x70
> [ 15.683279] dump_stack_lvl+0x9c/0xd8
> [ 15.683288] dump_stack+0x18/0x34
> [ 15.683289] __might_resched+0x188/0x228
> [ 15.683292] rt_spin_lock+0x70/0x120
> [ 15.683301] sdei_cpuhp_up+0x3c/0x130
> [ 15.683303] cpuhp_invoke_callback+0x250/0xf08
> [ 15.683305] cpuhp_thread_fun+0x120/0x248
> [ 15.683308] smpboot_thread_fn+0x280/0x320
> [ 15.683315] kthread+0x130/0x140
> [ 15.683321] ret_from_fork+0x10/0x20
>
> sdei_cpuhp_up() is called in the STARTING hotplug section,
> which runs whith interrupts disabled. Move CPUHP_AP_ARM_SDEI_
> state to the _ONLINE section to execute the cpuhp cb with
> preemption enabled.
>
> Some SDEI calls (e.g. SDEI_1_0_FN_SDEI_PE_MASK) take actions on the
> calling CPU. It is checked that preemption is disabled for them.
> _ONLINE cpuhp cb are executed in the 'per CPU hotplug thread'.
> Preemption is enabled in those threads, but their cpumask is limited
> to 1 CPU.
> Move 'WARN_ON_ONCE(preemptible())' statements so that SDEI cpuhp cb
> don't trigger them. This means that no check will be done for some
> cases, e.g. sdei_mask_local_cpu() invocations.
>
> Also add a check for the SDEI_1_0_FN_SDEI_PRIVATE_RESET SDEI call
> which acts on the calling CPU.
>
> Suggested-by: James Morse <[email protected]>
> Signed-off-by: Pierre Gondois <[email protected]>
> ---
> drivers/firmware/arm_sdei.c | 28 ++++++++++++++--------------
> include/linux/cpuhotplug.h | 2 +-
> 2 files changed, 15 insertions(+), 15 deletions(-)
James -- are you taking care of this one, or should I queue it via arm64?
Will
Hi Pierre,
Sorry its taken so long for me to catch up with this ...
On 18/10/2022 14:04, Pierre Gondois wrote:
> On an Ampere Altra,
> Running a preemp_rt kernel based on v5.19-rc3-rt5 on an
> Ampere Altra triggers:
> [ 15.683141] BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:46
> [ 15.683154] in_atomic(): 0, irqs_disabled(): 128, non_block: 0, pid: 24, name: cpuhp/0
> [ 15.683157] preempt_count: 0, expected: 0
> [ 15.683159] RCU nest depth: 0, expected: 0
> [ 15.683163] 3 locks held by cpuhp/0/24:
> [ 15.683167] #0: ffffda30217c70d0 (cpu_hotplug_lock){++++}-{0:0}, at: cpuhp_thread_fun+0x5c/0x248
> [ 15.683201] #1: ffffda30217c7120 (cpuhp_state-up){+.+.}-{0:0}, at: cpuhp_thread_fun+0x5c/0x248
> [ 15.683205] #2: ffffda3021c711f0 (sdei_list_lock){....}-{3:3}, at: sdei_cpuhp_up+0x3c/0x130
> [ 15.683224] irq event stamp: 36
> [ 15.683226] hardirqs last enabled at (35): [<ffffda301e85b7bc>] finish_task_switch+0xb4/0x2b0
> [ 15.683236] hardirqs last disabled at (36): [<ffffda301e812fec>] cpuhp_thread_fun+0x21c/0x248
> [ 15.683238] softirqs last enabled at (0): [<ffffda301e80b184>] copy_process+0x63c/0x1ac0
> [ 15.683245] softirqs last disabled at (0): [<0000000000000000>] 0x0
> [ 15.683258] CPU: 0 PID: 24 Comm: cpuhp/0 Not tainted 5.19.0-rc3-rt5-[...]
> [ 15.683265] Hardware name: WIWYNN Mt.Jade Server System B81.03001.0005/Mt.Jade Motherboard, BIOS 1.08.20220218 (SCP: 1.08.20220218) 2022/02/18
> [ 15.683268] Call trace:
> [ 15.683271] dump_backtrace+0x114/0x120
> [ 15.683277] show_stack+0x20/0x70
> [ 15.683279] dump_stack_lvl+0x9c/0xd8
> [ 15.683288] dump_stack+0x18/0x34
> [ 15.683289] __might_resched+0x188/0x228
> [ 15.683292] rt_spin_lock+0x70/0x120
> [ 15.683301] sdei_cpuhp_up+0x3c/0x130
> [ 15.683303] cpuhp_invoke_callback+0x250/0xf08
> [ 15.683305] cpuhp_thread_fun+0x120/0x248
> [ 15.683308] smpboot_thread_fn+0x280/0x320
> [ 15.683315] kthread+0x130/0x140
> [ 15.683321] ret_from_fork+0x10/0x20
> sdei_cpuhp_up() is called in the STARTING hotplug section,
> which runs whith interrupts disabled. Move CPUHP_AP_ARM_SDEI_
> state to the _ONLINE section to execute the cpuhp cb with
> preemption enabled.
The background to this is SDEI got its own cpuhp slot because 'perf NMI' support
was one of the use-cases, but this got superseded by pNMI. Without an interaction with
perf, the slot doesn't need to be that early.
> Some SDEI calls (e.g. SDEI_1_0_FN_SDEI_PE_MASK) take actions on the
> calling CPU. It is checked that preemption is disabled for them.
> _ONLINE cpuhp cb are executed in the 'per CPU hotplug thread'.
> Preemption is enabled in those threads, but their cpumask is limited
> to 1 CPU.
> Move 'WARN_ON_ONCE(preemptible())' statements so that SDEI cpuhp cb
> don't trigger them. This means that no check will be done for some
> cases, e.g. sdei_mask_local_cpu() invocations.
(these things are documentation anyway)
> Also add a check for the SDEI_1_0_FN_SDEI_PRIVATE_RESET SDEI call
> which acts on the calling CPU.
> diff --git a/drivers/firmware/arm_sdei.c b/drivers/firmware/arm_sdei.c
> index 1e1a51510e83..9b03e164a37a 100644
> --- a/drivers/firmware/arm_sdei.c
> +++ b/drivers/firmware/arm_sdei.c
> @@ -401,6 +399,8 @@ int sdei_event_enable(u32 event_num)
> int err = -EINVAL;
> struct sdei_event *event;
>
> + WARN_ON_ONCE(preemptible());
> +
> mutex_lock(&sdei_events_lock);
> event = sdei_event_find(event_num);
> if (!event) {
This doesn't look right. How can this code take a mutex if its in a non-preemptable context?
> @@ -492,6 +490,7 @@ int sdei_event_unregister(u32 event_num)
> struct sdei_event *event;
>
> WARN_ON(in_nmi());
> + WARN_ON_ONCE(preemptible());
>
> mutex_lock(&sdei_events_lock);
> event = sdei_event_find(event_num);
Same again.
> @@ -576,6 +573,7 @@ int sdei_event_register(u32 event_num, sdei_event_callback *cb, void *arg)
> struct sdei_event *event;
>
> WARN_ON(in_nmi());
> + WARN_ON_ONCE(preemptible());
>
> mutex_lock(&sdei_events_lock);
> if (sdei_event_find(event_num)) {
Same again.
I think you've copied these here because they called _local_event_unregister(), but they
did that via on_each_cpu(), which is what made _local_event_unregister() non-preemtable.
You can just remove these three, the original warnings were mostly documentation, and to
catch myself out. (before RT moved the goal posts).
With that:
Reviewed-by: James Morse <[email protected]>
(could you trim the [timestamps] out of the commit log?)
> @@ -765,7 +765,7 @@ static int sdei_device_freeze(struct device *dev)
> int err;
>
> /* unregister private events */
> - cpuhp_remove_state(CPUHP_AP_ARM_SDEI_STARTING);
> + cpuhp_remove_state(CPUHP_AP_ARM_SDEI_ONLINE);
Is there any mileage in making this CPUHP_AP_ONLINE_DYN ?
Perf really was the only reason that this needed to happen in any particular order.
Thanks,
James
Hello James,
On 2/10/23 18:42, James Morse wrote:
> Hi Pierre,
>
> Sorry its taken so long for me to catch up with this ...
No worries.
>
> On 18/10/2022 14:04, Pierre Gondois wrote:
>> On an Ampere Altra,
>> Running a preemp_rt kernel based on v5.19-rc3-rt5 on an
>> Ampere Altra triggers:
>> [ 15.683141] BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:46
>> [ 15.683154] in_atomic(): 0, irqs_disabled(): 128, non_block: 0, pid: 24, name: cpuhp/0
>> [ 15.683157] preempt_count: 0, expected: 0
>> [ 15.683159] RCU nest depth: 0, expected: 0
>> [ 15.683163] 3 locks held by cpuhp/0/24:
>> [ 15.683167] #0: ffffda30217c70d0 (cpu_hotplug_lock){++++}-{0:0}, at: cpuhp_thread_fun+0x5c/0x248
>> [ 15.683201] #1: ffffda30217c7120 (cpuhp_state-up){+.+.}-{0:0}, at: cpuhp_thread_fun+0x5c/0x248
>> [ 15.683205] #2: ffffda3021c711f0 (sdei_list_lock){....}-{3:3}, at: sdei_cpuhp_up+0x3c/0x130
>> [ 15.683224] irq event stamp: 36
>> [ 15.683226] hardirqs last enabled at (35): [<ffffda301e85b7bc>] finish_task_switch+0xb4/0x2b0
>> [ 15.683236] hardirqs last disabled at (36): [<ffffda301e812fec>] cpuhp_thread_fun+0x21c/0x248
>> [ 15.683238] softirqs last enabled at (0): [<ffffda301e80b184>] copy_process+0x63c/0x1ac0
>> [ 15.683245] softirqs last disabled at (0): [<0000000000000000>] 0x0
>> [ 15.683258] CPU: 0 PID: 24 Comm: cpuhp/0 Not tainted 5.19.0-rc3-rt5-[...]
>> [ 15.683265] Hardware name: WIWYNN Mt.Jade Server System B81.03001.0005/Mt.Jade Motherboard, BIOS 1.08.20220218 (SCP: 1.08.20220218) 2022/02/18
>> [ 15.683268] Call trace:
>> [ 15.683271] dump_backtrace+0x114/0x120
>> [ 15.683277] show_stack+0x20/0x70
>> [ 15.683279] dump_stack_lvl+0x9c/0xd8
>> [ 15.683288] dump_stack+0x18/0x34
>> [ 15.683289] __might_resched+0x188/0x228
>> [ 15.683292] rt_spin_lock+0x70/0x120
>> [ 15.683301] sdei_cpuhp_up+0x3c/0x130
>> [ 15.683303] cpuhp_invoke_callback+0x250/0xf08
>> [ 15.683305] cpuhp_thread_fun+0x120/0x248
>> [ 15.683308] smpboot_thread_fn+0x280/0x320
>> [ 15.683315] kthread+0x130/0x140
>> [ 15.683321] ret_from_fork+0x10/0x20
>
>> sdei_cpuhp_up() is called in the STARTING hotplug section,
>> which runs whith interrupts disabled. Move CPUHP_AP_ARM_SDEI_
>> state to the _ONLINE section to execute the cpuhp cb with
>> preemption enabled.
>
> The background to this is SDEI got its own cpuhp slot because 'perf NMI' support
> was one of the use-cases, but this got superseded by pNMI. Without an interaction with
> perf, the slot doesn't need to be that early.
>
>
>> Some SDEI calls (e.g. SDEI_1_0_FN_SDEI_PE_MASK) take actions on the
>> calling CPU. It is checked that preemption is disabled for them.
>> _ONLINE cpuhp cb are executed in the 'per CPU hotplug thread'.
>> Preemption is enabled in those threads, but their cpumask is limited
>> to 1 CPU.
>
>> Move 'WARN_ON_ONCE(preemptible())' statements so that SDEI cpuhp cb
>> don't trigger them. This means that no check will be done for some
>> cases, e.g. sdei_mask_local_cpu() invocations.
>
> (these things are documentation anyway)
>
>
>> Also add a check for the SDEI_1_0_FN_SDEI_PRIVATE_RESET SDEI call
>> which acts on the calling CPU.
>
>> diff --git a/drivers/firmware/arm_sdei.c b/drivers/firmware/arm_sdei.c
>> index 1e1a51510e83..9b03e164a37a 100644
>> --- a/drivers/firmware/arm_sdei.c
>> +++ b/drivers/firmware/arm_sdei.c
>
>> @@ -401,6 +399,8 @@ int sdei_event_enable(u32 event_num)
>> int err = -EINVAL;
>> struct sdei_event *event;
>>
>> + WARN_ON_ONCE(preemptible());
>> +
>> mutex_lock(&sdei_events_lock);
>> event = sdei_event_find(event_num);
>> if (!event) {
>
> This doesn't look right. How can this code take a mutex if its in a non-preemptable context?
>
>> @@ -492,6 +490,7 @@ int sdei_event_unregister(u32 event_num)
>> struct sdei_event *event;
>>
>> WARN_ON(in_nmi());
>> + WARN_ON_ONCE(preemptible());
>>
>> mutex_lock(&sdei_events_lock);
>> event = sdei_event_find(event_num);
>
> Same again.
>
>> @@ -576,6 +573,7 @@ int sdei_event_register(u32 event_num, sdei_event_callback *cb, void *arg)
>> struct sdei_event *event;
>>
>> WARN_ON(in_nmi());
>> + WARN_ON_ONCE(preemptible());
>>
>> mutex_lock(&sdei_events_lock);
>> if (sdei_event_find(event_num)) {
>
> Same again.
>
> I think you've copied these here because they called _local_event_unregister(), but they
> did that via on_each_cpu(), which is what made _local_event_unregister() non-preemtable.
Yes right, these 3 warnings don't really make sense. They will be removed.
>
> You can just remove these three, the original warnings were mostly documentation, and to
> catch myself out. (before RT moved the goal posts).
>
> With that:
> Reviewed-by: James Morse <[email protected]>
>
> (could you trim the [timestamps] out of the commit log?)
Yes sure.
>
>
>> @@ -765,7 +765,7 @@ static int sdei_device_freeze(struct device *dev)
>> int err;
>>
>> /* unregister private events */
>> - cpuhp_remove_state(CPUHP_AP_ARM_SDEI_STARTING);
>> + cpuhp_remove_state(CPUHP_AP_ARM_SDEI_ONLINE);
>
> Is there any mileage in making this CPUHP_AP_ONLINE_DYN ?
> Perf really was the only reason that this needed to happen in any particular order.
Ok I will do that.
Thanks for the review,
Regards,
Pierre
>
>
> Thanks,
>
> James