* [PATCH] arm64/cpufeature: Convert hook_lock to raw_spin_lock_t in cpu_enable_ssbs()
@ 2019-05-30 11:30 ` Julien Grall
0 siblings, 0 replies; 8+ messages in thread
From: Julien Grall @ 2019-05-30 11:30 UTC (permalink / raw)
To: linux-kernel, linux-rt-users, linux-arm-kernel
Cc: tglx, rostedt, bigeasy, suzuki.poulose, catalin.marinas,
will.deacon, dave.martin, Julien Grall
cpu_enable_ssbs() is called via stop_machine() as part of the cpu_enable
callback. A spin lock is used to ensure the hook is registered before
the rest of the callback is executed.
On -RT spin_lock() may sleep. However, all the callees in stop_machine()
are expected to not sleep. Therefore a raw_spin_lock() is required here.
Given this is already done under stop_machine() and the work done under
the lock is quite small, the latency should not increase too much.
Signed-off-by: Julien Grall <julien.grall@arm.com>
---
It was noticed when looking at the current use of spin_lock in
arch/arm64. I don't have a platform calling that callback, so I have
hacked the code to reproduce the error and check it is now fixed.
---
arch/arm64/kernel/cpufeature.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index ca27e08e3d8a..2a7159fda3ce 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1194,14 +1194,14 @@ static struct undef_hook ssbs_emulation_hook = {
static void cpu_enable_ssbs(const struct arm64_cpu_capabilities *__unused)
{
static bool undef_hook_registered = false;
- static DEFINE_SPINLOCK(hook_lock);
+ static DEFINE_RAW_SPINLOCK(hook_lock);
- spin_lock(&hook_lock);
+ raw_spin_lock(&hook_lock);
if (!undef_hook_registered) {
register_undef_hook(&ssbs_emulation_hook);
undef_hook_registered = true;
}
- spin_unlock(&hook_lock);
+ raw_spin_unlock(&hook_lock);
if (arm64_get_ssbd_state() == ARM64_SSBD_FORCE_DISABLE) {
sysreg_clear_set(sctlr_el1, 0, SCTLR_ELx_DSSBS);
--
2.11.0
^ permalink raw reply related [flat|nested] 8+ messages in thread
* [PATCH] arm64/cpufeature: Convert hook_lock to raw_spin_lock_t in cpu_enable_ssbs()
@ 2019-05-30 11:30 ` Julien Grall
0 siblings, 0 replies; 8+ messages in thread
From: Julien Grall @ 2019-05-30 11:30 UTC (permalink / raw)
To: linux-kernel, linux-rt-users, linux-arm-kernel
Cc: suzuki.poulose, catalin.marinas, bigeasy, will.deacon, rostedt,
Julien Grall, tglx, dave.martin
cpu_enable_ssbs() is called via stop_machine() as part of the cpu_enable
callback. A spin lock is used to ensure the hook is registered before
the rest of the callback is executed.
On -RT spin_lock() may sleep. However, all the callees in stop_machine()
are expected to not sleep. Therefore a raw_spin_lock() is required here.
Given this is already done under stop_machine() and the work done under
the lock is quite small, the latency should not increase too much.
Signed-off-by: Julien Grall <julien.grall@arm.com>
---
It was noticed when looking at the current use of spin_lock in
arch/arm64. I don't have a platform calling that callback, so I have
hacked the code to reproduce the error and check it is now fixed.
---
arch/arm64/kernel/cpufeature.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index ca27e08e3d8a..2a7159fda3ce 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -1194,14 +1194,14 @@ static struct undef_hook ssbs_emulation_hook = {
static void cpu_enable_ssbs(const struct arm64_cpu_capabilities *__unused)
{
static bool undef_hook_registered = false;
- static DEFINE_SPINLOCK(hook_lock);
+ static DEFINE_RAW_SPINLOCK(hook_lock);
- spin_lock(&hook_lock);
+ raw_spin_lock(&hook_lock);
if (!undef_hook_registered) {
register_undef_hook(&ssbs_emulation_hook);
undef_hook_registered = true;
}
- spin_unlock(&hook_lock);
+ raw_spin_unlock(&hook_lock);
if (arm64_get_ssbd_state() == ARM64_SSBD_FORCE_DISABLE) {
sysreg_clear_set(sctlr_el1, 0, SCTLR_ELx_DSSBS);
--
2.11.0
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply related [flat|nested] 8+ messages in thread
* Re: [PATCH] arm64/cpufeature: Convert hook_lock to raw_spin_lock_t in cpu_enable_ssbs()
2019-05-30 11:30 ` Julien Grall
@ 2019-05-30 12:01 ` Will Deacon
-1 siblings, 0 replies; 8+ messages in thread
From: Will Deacon @ 2019-05-30 12:01 UTC (permalink / raw)
To: Julien Grall
Cc: linux-kernel, linux-rt-users, linux-arm-kernel, tglx, rostedt,
bigeasy, suzuki.poulose, catalin.marinas, dave.martin
On Thu, May 30, 2019 at 12:30:58PM +0100, Julien Grall wrote:
> cpu_enable_ssbs() is called via stop_machine() as part of the cpu_enable
> callback. A spin lock is used to ensure the hook is registered before
> the rest of the callback is executed.
>
> On -RT spin_lock() may sleep. However, all the callees in stop_machine()
> are expected to not sleep. Therefore a raw_spin_lock() is required here.
>
> Given this is already done under stop_machine() and the work done under
> the lock is quite small, the latency should not increase too much.
>
> Signed-off-by: Julien Grall <julien.grall@arm.com>
>
> ---
>
> It was noticed when looking at the current use of spin_lock in
> arch/arm64. I don't have a platform calling that callback, so I have
> hacked the code to reproduce the error and check it is now fixed.
> ---
> arch/arm64/kernel/cpufeature.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index ca27e08e3d8a..2a7159fda3ce 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -1194,14 +1194,14 @@ static struct undef_hook ssbs_emulation_hook = {
> static void cpu_enable_ssbs(const struct arm64_cpu_capabilities *__unused)
> {
> static bool undef_hook_registered = false;
> - static DEFINE_SPINLOCK(hook_lock);
> + static DEFINE_RAW_SPINLOCK(hook_lock);
>
> - spin_lock(&hook_lock);
> + raw_spin_lock(&hook_lock);
> if (!undef_hook_registered) {
> register_undef_hook(&ssbs_emulation_hook);
> undef_hook_registered = true;
> }
> - spin_unlock(&hook_lock);
> + raw_spin_unlock(&hook_lock);
Makes sense to me. We could probably avoid the lock entirely if we wanted
to (via atomic_dec_if_positive), but I'm not sure it's really worth it.
Will
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] arm64/cpufeature: Convert hook_lock to raw_spin_lock_t in cpu_enable_ssbs()
@ 2019-05-30 12:01 ` Will Deacon
0 siblings, 0 replies; 8+ messages in thread
From: Will Deacon @ 2019-05-30 12:01 UTC (permalink / raw)
To: Julien Grall
Cc: linux-rt-users, suzuki.poulose, catalin.marinas, bigeasy,
linux-kernel, rostedt, tglx, dave.martin, linux-arm-kernel
On Thu, May 30, 2019 at 12:30:58PM +0100, Julien Grall wrote:
> cpu_enable_ssbs() is called via stop_machine() as part of the cpu_enable
> callback. A spin lock is used to ensure the hook is registered before
> the rest of the callback is executed.
>
> On -RT spin_lock() may sleep. However, all the callees in stop_machine()
> are expected to not sleep. Therefore a raw_spin_lock() is required here.
>
> Given this is already done under stop_machine() and the work done under
> the lock is quite small, the latency should not increase too much.
>
> Signed-off-by: Julien Grall <julien.grall@arm.com>
>
> ---
>
> It was noticed when looking at the current use of spin_lock in
> arch/arm64. I don't have a platform calling that callback, so I have
> hacked the code to reproduce the error and check it is now fixed.
> ---
> arch/arm64/kernel/cpufeature.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index ca27e08e3d8a..2a7159fda3ce 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -1194,14 +1194,14 @@ static struct undef_hook ssbs_emulation_hook = {
> static void cpu_enable_ssbs(const struct arm64_cpu_capabilities *__unused)
> {
> static bool undef_hook_registered = false;
> - static DEFINE_SPINLOCK(hook_lock);
> + static DEFINE_RAW_SPINLOCK(hook_lock);
>
> - spin_lock(&hook_lock);
> + raw_spin_lock(&hook_lock);
> if (!undef_hook_registered) {
> register_undef_hook(&ssbs_emulation_hook);
> undef_hook_registered = true;
> }
> - spin_unlock(&hook_lock);
> + raw_spin_unlock(&hook_lock);
Makes sense to me. We could probably avoid the lock entirely if we wanted
to (via atomic_dec_if_positive), but I'm not sure it's really worth it.
Will
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] arm64/cpufeature: Convert hook_lock to raw_spin_lock_t in cpu_enable_ssbs()
2019-05-30 12:01 ` Will Deacon
@ 2019-05-30 13:55 ` Julien Grall
-1 siblings, 0 replies; 8+ messages in thread
From: Julien Grall @ 2019-05-30 13:55 UTC (permalink / raw)
To: Will Deacon
Cc: linux-kernel, linux-rt-users, linux-arm-kernel, tglx, rostedt,
bigeasy, suzuki.poulose, catalin.marinas, dave.martin
Hi Will,
On 5/30/19 1:01 PM, Will Deacon wrote:
> On Thu, May 30, 2019 at 12:30:58PM +0100, Julien Grall wrote:
>> cpu_enable_ssbs() is called via stop_machine() as part of the cpu_enable
>> callback. A spin lock is used to ensure the hook is registered before
>> the rest of the callback is executed.
>>
>> On -RT spin_lock() may sleep. However, all the callees in stop_machine()
>> are expected to not sleep. Therefore a raw_spin_lock() is required here.
>>
>> Given this is already done under stop_machine() and the work done under
>> the lock is quite small, the latency should not increase too much.
>>
>> Signed-off-by: Julien Grall <julien.grall@arm.com>
>>
>> ---
>>
>> It was noticed when looking at the current use of spin_lock in
>> arch/arm64. I don't have a platform calling that callback, so I have
>> hacked the code to reproduce the error and check it is now fixed.
>> ---
>> arch/arm64/kernel/cpufeature.c | 6 +++---
>> 1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
>> index ca27e08e3d8a..2a7159fda3ce 100644
>> --- a/arch/arm64/kernel/cpufeature.c
>> +++ b/arch/arm64/kernel/cpufeature.c
>> @@ -1194,14 +1194,14 @@ static struct undef_hook ssbs_emulation_hook = {
>> static void cpu_enable_ssbs(const struct arm64_cpu_capabilities *__unused)
>> {
>> static bool undef_hook_registered = false;
>> - static DEFINE_SPINLOCK(hook_lock);
>> + static DEFINE_RAW_SPINLOCK(hook_lock);
>>
>> - spin_lock(&hook_lock);
>> + raw_spin_lock(&hook_lock);
>> if (!undef_hook_registered) {
>> register_undef_hook(&ssbs_emulation_hook);
>> undef_hook_registered = true;
>> }
>> - spin_unlock(&hook_lock);
>> + raw_spin_unlock(&hook_lock);
>
> Makes sense to me. We could probably avoid the lock entirely if we wanted
> to (via atomic_dec_if_positive), but I'm not sure it's really worth it.
I would prefer to remove the lock if it is possible. However, I was
under the impression the lock is necessary so the hook is registered
before any CPU attempt to configure the PSTATE.
Cheers,
--
Julien Grall
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] arm64/cpufeature: Convert hook_lock to raw_spin_lock_t in cpu_enable_ssbs()
@ 2019-05-30 13:55 ` Julien Grall
0 siblings, 0 replies; 8+ messages in thread
From: Julien Grall @ 2019-05-30 13:55 UTC (permalink / raw)
To: Will Deacon
Cc: linux-rt-users, suzuki.poulose, catalin.marinas, bigeasy,
linux-kernel, rostedt, tglx, dave.martin, linux-arm-kernel
Hi Will,
On 5/30/19 1:01 PM, Will Deacon wrote:
> On Thu, May 30, 2019 at 12:30:58PM +0100, Julien Grall wrote:
>> cpu_enable_ssbs() is called via stop_machine() as part of the cpu_enable
>> callback. A spin lock is used to ensure the hook is registered before
>> the rest of the callback is executed.
>>
>> On -RT spin_lock() may sleep. However, all the callees in stop_machine()
>> are expected to not sleep. Therefore a raw_spin_lock() is required here.
>>
>> Given this is already done under stop_machine() and the work done under
>> the lock is quite small, the latency should not increase too much.
>>
>> Signed-off-by: Julien Grall <julien.grall@arm.com>
>>
>> ---
>>
>> It was noticed when looking at the current use of spin_lock in
>> arch/arm64. I don't have a platform calling that callback, so I have
>> hacked the code to reproduce the error and check it is now fixed.
>> ---
>> arch/arm64/kernel/cpufeature.c | 6 +++---
>> 1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
>> index ca27e08e3d8a..2a7159fda3ce 100644
>> --- a/arch/arm64/kernel/cpufeature.c
>> +++ b/arch/arm64/kernel/cpufeature.c
>> @@ -1194,14 +1194,14 @@ static struct undef_hook ssbs_emulation_hook = {
>> static void cpu_enable_ssbs(const struct arm64_cpu_capabilities *__unused)
>> {
>> static bool undef_hook_registered = false;
>> - static DEFINE_SPINLOCK(hook_lock);
>> + static DEFINE_RAW_SPINLOCK(hook_lock);
>>
>> - spin_lock(&hook_lock);
>> + raw_spin_lock(&hook_lock);
>> if (!undef_hook_registered) {
>> register_undef_hook(&ssbs_emulation_hook);
>> undef_hook_registered = true;
>> }
>> - spin_unlock(&hook_lock);
>> + raw_spin_unlock(&hook_lock);
>
> Makes sense to me. We could probably avoid the lock entirely if we wanted
> to (via atomic_dec_if_positive), but I'm not sure it's really worth it.
I would prefer to remove the lock if it is possible. However, I was
under the impression the lock is necessary so the hook is registered
before any CPU attempt to configure the PSTATE.
Cheers,
--
Julien Grall
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] arm64/cpufeature: Convert hook_lock to raw_spin_lock_t in cpu_enable_ssbs()
2019-05-30 11:30 ` Julien Grall
@ 2019-06-04 13:49 ` Catalin Marinas
-1 siblings, 0 replies; 8+ messages in thread
From: Catalin Marinas @ 2019-06-04 13:49 UTC (permalink / raw)
To: Julien Grall
Cc: linux-kernel, linux-rt-users, linux-arm-kernel, tglx, rostedt,
bigeasy, suzuki.poulose, will.deacon, dave.martin
On Thu, May 30, 2019 at 12:30:58PM +0100, Julien Grall wrote:
> cpu_enable_ssbs() is called via stop_machine() as part of the cpu_enable
> callback. A spin lock is used to ensure the hook is registered before
> the rest of the callback is executed.
>
> On -RT spin_lock() may sleep. However, all the callees in stop_machine()
> are expected to not sleep. Therefore a raw_spin_lock() is required here.
>
> Given this is already done under stop_machine() and the work done under
> the lock is quite small, the latency should not increase too much.
>
> Signed-off-by: Julien Grall <julien.grall@arm.com>
Queued for 5.3. Thanks.
--
Catalin
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] arm64/cpufeature: Convert hook_lock to raw_spin_lock_t in cpu_enable_ssbs()
@ 2019-06-04 13:49 ` Catalin Marinas
0 siblings, 0 replies; 8+ messages in thread
From: Catalin Marinas @ 2019-06-04 13:49 UTC (permalink / raw)
To: Julien Grall
Cc: linux-rt-users, suzuki.poulose, bigeasy, will.deacon,
linux-kernel, rostedt, tglx, dave.martin, linux-arm-kernel
On Thu, May 30, 2019 at 12:30:58PM +0100, Julien Grall wrote:
> cpu_enable_ssbs() is called via stop_machine() as part of the cpu_enable
> callback. A spin lock is used to ensure the hook is registered before
> the rest of the callback is executed.
>
> On -RT spin_lock() may sleep. However, all the callees in stop_machine()
> are expected to not sleep. Therefore a raw_spin_lock() is required here.
>
> Given this is already done under stop_machine() and the work done under
> the lock is quite small, the latency should not increase too much.
>
> Signed-off-by: Julien Grall <julien.grall@arm.com>
Queued for 5.3. Thanks.
--
Catalin
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2019-06-04 13:49 UTC | newest]
Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-05-30 11:30 [PATCH] arm64/cpufeature: Convert hook_lock to raw_spin_lock_t in cpu_enable_ssbs() Julien Grall
2019-05-30 11:30 ` Julien Grall
2019-05-30 12:01 ` Will Deacon
2019-05-30 12:01 ` Will Deacon
2019-05-30 13:55 ` Julien Grall
2019-05-30 13:55 ` Julien Grall
2019-06-04 13:49 ` Catalin Marinas
2019-06-04 13:49 ` Catalin Marinas
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