Re: [PATCH AUTOSEL for 4.15 104/124] clk: fix reentrancy of clk_enable() on UP systems

[Sasha Levin]

On Mon, Mar 19, 2018 at 10:55:16AM -0500, David Lechner wrote:
>On 03/19/2018 10:48 AM, Sasha Levin wrote:
>>From: David Lechner 
>>
>>[ Upstream commit a12aa8a68dfef5de181f2e555aa950a0ab05411f ]
>>
>>Reentrant calls to clk_enable() are not working on UP systems. This is
>>caused by the fact spin_trylock_irqsave() always returns true when
>>CONFIG_SMP=n (and CONFIG_DEBUG_SPINLOCK=n) which causes the reference
>>counting to not work correctly when clk_enable_lock() is called twice
>>before clk_enable_unlock() is called (this happens when clk_enable()
>>is called from within another clk_enable()).
>>
>>This fixes the problem by skipping the call to spin_trylock_irqsave() on UP
>>systems and relying solely on reference counting. We also make sure to set
>>flags in this case so that we are not returning an uninitialized value.
>>
>>Suggested-by: Stephen Boyd 
>>Signed-off-by: David Lechner 
>>Signed-off-by: Stephen Boyd 
>>Signed-off-by: Sasha Levin 
>>---
>
>I don't know of any existing bugs in v4.15 that this fixes, so I don't
>think this really fits the criteria for stable.
>

Now removed, thanks!

Re: [PATCH AUTOSEL for 4.15 104/124] clk: fix reentrancy of clk_enable() on UP systems

[Sasha Levin]

On Mon, Mar 19, 2018 at 10:55:16AM -0500, David Lechner wrote:
>On 03/19/2018 10:48 AM, Sasha Levin wrote:
>>From: David Lechner 
>>
>>[ Upstream commit a12aa8a68dfef5de181f2e555aa950a0ab05411f ]
>>
>>Reentrant calls to clk_enable() are not working on UP systems. This is
>>caused by the fact spin_trylock_irqsave() always returns true when
>>CONFIG_SMP=n (and CONFIG_DEBUG_SPINLOCK=n) which causes the reference
>>counting to not work correctly when clk_enable_lock() is called twice
>>before clk_enable_unlock() is called (this happens when clk_enable()
>>is called from within another clk_enable()).
>>
>>This fixes the problem by skipping the call to spin_trylock_irqsave() on UP
>>systems and relying solely on reference counting. We also make sure to set
>>flags in this case so that we are not returning an uninitialized value.
>>
>>Suggested-by: Stephen Boyd 
>>Signed-off-by: David Lechner 
>>Signed-off-by: Stephen Boyd 
>>Signed-off-by: Sasha Levin 
>>---
>
>I don't know of any existing bugs in v4.15 that this fixes, so I don't
>think this really fits the criteria for stable.
>

Now removed, thanks!

[PATCH AUTOSEL for 4.15 104/124] clk: fix reentrancy of clk_enable() on UP systems

[Sasha Levin]

From: David Lechner 

[ Upstream commit a12aa8a68dfef5de181f2e555aa950a0ab05411f ]

Reentrant calls to clk_enable() are not working on UP systems. This is
caused by the fact spin_trylock_irqsave() always returns true when
CONFIG_SMP=n (and CONFIG_DEBUG_SPINLOCK=n) which causes the reference
counting to not work correctly when clk_enable_lock() is called twice
before clk_enable_unlock() is called (this happens when clk_enable()
is called from within another clk_enable()).

This fixes the problem by skipping the call to spin_trylock_irqsave() on UP
systems and relying solely on reference counting. We also make sure to set
flags in this case so that we are not returning an uninitialized value.

Suggested-by: Stephen Boyd 
Signed-off-by: David Lechner 
Signed-off-by: Stephen Boyd 
Signed-off-by: Sasha Levin 
---
 drivers/clk/clk.c | 10 +-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index b56c11f51baf..a6575359de58 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -141,10 +141,18 @@ static unsigned long clk_enable_lock(void)
 {
unsigned long flags;
 
-   if (!spin_trylock_irqsave(_lock, flags)) {
+   /*
+* On UP systems, spin_trylock_irqsave() always returns true, even if
+* we already hold the lock. So, in that case, we rely only on
+* reference counting.
+*/
+   if (!IS_ENABLED(CONFIG_SMP) ||
+   !spin_trylock_irqsave(_lock, flags)) {
if (enable_owner == current) {
enable_refcnt++;
__acquire(enable_lock);
+   if (!IS_ENABLED(CONFIG_SMP))
+   local_save_flags(flags);
return flags;
}
spin_lock_irqsave(_lock, flags);
-- 
2.14.1

[PATCH AUTOSEL for 4.15 104/124] clk: fix reentrancy of clk_enable() on UP systems

[Sasha Levin]

From: David Lechner 

[ Upstream commit a12aa8a68dfef5de181f2e555aa950a0ab05411f ]

Reentrant calls to clk_enable() are not working on UP systems. This is
caused by the fact spin_trylock_irqsave() always returns true when
CONFIG_SMP=n (and CONFIG_DEBUG_SPINLOCK=n) which causes the reference
counting to not work correctly when clk_enable_lock() is called twice
before clk_enable_unlock() is called (this happens when clk_enable()
is called from within another clk_enable()).

This fixes the problem by skipping the call to spin_trylock_irqsave() on UP
systems and relying solely on reference counting. We also make sure to set
flags in this case so that we are not returning an uninitialized value.

Suggested-by: Stephen Boyd 
Signed-off-by: David Lechner 
Signed-off-by: Stephen Boyd 
Signed-off-by: Sasha Levin 
---
 drivers/clk/clk.c | 10 +-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index b56c11f51baf..a6575359de58 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -141,10 +141,18 @@ static unsigned long clk_enable_lock(void)
 {
unsigned long flags;
 
-   if (!spin_trylock_irqsave(_lock, flags)) {
+   /*
+* On UP systems, spin_trylock_irqsave() always returns true, even if
+* we already hold the lock. So, in that case, we rely only on
+* reference counting.
+*/
+   if (!IS_ENABLED(CONFIG_SMP) ||
+   !spin_trylock_irqsave(_lock, flags)) {
if (enable_owner == current) {
enable_refcnt++;
__acquire(enable_lock);
+   if (!IS_ENABLED(CONFIG_SMP))
+   local_save_flags(flags);
return flags;
}
spin_lock_irqsave(_lock, flags);
-- 
2.14.1

Re: [PATCH AUTOSEL for 4.15 104/124] clk: fix reentrancy of clk_enable() on UP systems

[David Lechner]

On 03/19/2018 10:48 AM, Sasha Levin wrote:

From: David Lechner 

[ Upstream commit a12aa8a68dfef5de181f2e555aa950a0ab05411f ]

Reentrant calls to clk_enable() are not working on UP systems. This is
caused by the fact spin_trylock_irqsave() always returns true when
CONFIG_SMP=n (and CONFIG_DEBUG_SPINLOCK=n) which causes the reference
counting to not work correctly when clk_enable_lock() is called twice
before clk_enable_unlock() is called (this happens when clk_enable()
is called from within another clk_enable()).

This fixes the problem by skipping the call to spin_trylock_irqsave() on UP
systems and relying solely on reference counting. We also make sure to set
flags in this case so that we are not returning an uninitialized value.

Suggested-by: Stephen Boyd 
Signed-off-by: David Lechner 
Signed-off-by: Stephen Boyd 
Signed-off-by: Sasha Levin 
---


I don't know of any existing bugs in v4.15 that this fixes, so I don't
think this really fits the criteria for stable.

Re: [PATCH AUTOSEL for 4.15 104/124] clk: fix reentrancy of clk_enable() on UP systems

[David Lechner]

On 03/19/2018 10:48 AM, Sasha Levin wrote:

From: David Lechner 

[ Upstream commit a12aa8a68dfef5de181f2e555aa950a0ab05411f ]

Reentrant calls to clk_enable() are not working on UP systems. This is
caused by the fact spin_trylock_irqsave() always returns true when
CONFIG_SMP=n (and CONFIG_DEBUG_SPINLOCK=n) which causes the reference
counting to not work correctly when clk_enable_lock() is called twice
before clk_enable_unlock() is called (this happens when clk_enable()
is called from within another clk_enable()).

This fixes the problem by skipping the call to spin_trylock_irqsave() on UP
systems and relying solely on reference counting. We also make sure to set
flags in this case so that we are not returning an uninitialized value.

Suggested-by: Stephen Boyd 
Signed-off-by: David Lechner 
Signed-off-by: Stephen Boyd 
Signed-off-by: Sasha Levin 
---


I don't know of any existing bugs in v4.15 that this fixes, so I don't
think this really fits the criteria for stable.

Re: [PATCH AUTOSEL for 4.15 104/124] clk: fix reentrancy of clk_enable() on UP systems

[Sasha Levin]

On Mon, Mar 19, 2018 at 10:55:16AM -0500, David Lechner wrote:
>On 03/19/2018 10:48 AM, Sasha Levin wrote:
>>From: David Lechner 
>>
>>[ Upstream commit a12aa8a68dfef5de181f2e555aa950a0ab05411f ]
>>
>>Reentrant calls to clk_enable() are not working on UP systems. This is
>>caused by the fact spin_trylock_irqsave() always returns true when
>>CONFIG_SMP=n (and CONFIG_DEBUG_SPINLOCK=n) which causes the reference
>>counting to not work correctly when clk_enable_lock() is called twice
>>before clk_enable_unlock() is called (this happens when clk_enable()
>>is called from within another clk_enable()).
>>
>>This fixes the problem by skipping the call to spin_trylock_irqsave() on UP
>>systems and relying solely on reference counting. We also make sure to set
>>flags in this case so that we are not returning an uninitialized value.
>>
>>Suggested-by: Stephen Boyd 
>>Signed-off-by: David Lechner 
>>Signed-off-by: Stephen Boyd 
>>Signed-off-by: Sasha Levin 
>>---
>
>I don't know of any existing bugs in v4.15 that this fixes, so I don't
>think this really fits the criteria for stable.
>

I'll remove it, thanks David!

-- 

Thanks,
Sasha

Re: [PATCH AUTOSEL for 4.15 104/124] clk: fix reentrancy of clk_enable() on UP systems

[Sasha Levin]

On Mon, Mar 19, 2018 at 10:55:16AM -0500, David Lechner wrote:
>On 03/19/2018 10:48 AM, Sasha Levin wrote:
>>From: David Lechner 
>>
>>[ Upstream commit a12aa8a68dfef5de181f2e555aa950a0ab05411f ]
>>
>>Reentrant calls to clk_enable() are not working on UP systems. This is
>>caused by the fact spin_trylock_irqsave() always returns true when
>>CONFIG_SMP=n (and CONFIG_DEBUG_SPINLOCK=n) which causes the reference
>>counting to not work correctly when clk_enable_lock() is called twice
>>before clk_enable_unlock() is called (this happens when clk_enable()
>>is called from within another clk_enable()).
>>
>>This fixes the problem by skipping the call to spin_trylock_irqsave() on UP
>>systems and relying solely on reference counting. We also make sure to set
>>flags in this case so that we are not returning an uninitialized value.
>>
>>Suggested-by: Stephen Boyd 
>>Signed-off-by: David Lechner 
>>Signed-off-by: Stephen Boyd 
>>Signed-off-by: Sasha Levin 
>>---
>
>I don't know of any existing bugs in v4.15 that this fixes, so I don't
>think this really fits the criteria for stable.
>

I'll remove it, thanks David!

-- 

Thanks,
Sasha