diff mbox series

mm, zsmalloc: Convert zsmalloc_handle.lock to spinlock_t

Message ID 70cc66840bbd9446061fc40088575565d8d98e37.camel@gmx.de
State New
Headers show
Series mm, zsmalloc: Convert zsmalloc_handle.lock to spinlock_t | expand

Commit Message

Mike Galbraith Aug. 24, 2021, 11:08 a.m. UTC 
local_lock_t becoming a synonym of spinlock_t had consequences for the RT
mods to zsmalloc, which were taking a mutex while holding a local_lock,
inspiring a lockdep "BUG: Invalid wait context" gripe.

Converting zsmalloc_handle.lock to a spinlock_t restored lockdep silence.

Signed-off-by: Mike Galbraith <efault@gmx.de>
---
 mm/zsmalloc.c |   12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

Comments

Vlastimil Babka Aug. 24, 2021, 11:14 a.m. UTC | #1 
On 8/24/21 13:08, Mike Galbraith wrote:
> 
> local_lock_t becoming a synonym of spinlock_t had consequences for the RT
> mods to zsmalloc, which were taking a mutex while holding a local_lock,
> inspiring a lockdep "BUG: Invalid wait context" gripe.
> 
> Converting zsmalloc_handle.lock to a spinlock_t restored lockdep silence.
> 
> Signed-off-by: Mike Galbraith <efault@gmx.de>

BTW, does anyone really run zswap on a RT system?
Sebastian Andrzej Siewior Aug. 26, 2021, 2:57 p.m. UTC | #2 
On 2021-08-24 13:14:52 [+0200], Vlastimil Babka wrote:
> On 8/24/21 13:08, Mike Galbraith wrote:

> > 

> > local_lock_t becoming a synonym of spinlock_t had consequences for the RT

> > mods to zsmalloc, which were taking a mutex while holding a local_lock,

> > inspiring a lockdep "BUG: Invalid wait context" gripe.

> > 

> > Converting zsmalloc_handle.lock to a spinlock_t restored lockdep silence.

> > 

> > Signed-off-by: Mike Galbraith <efault@gmx.de>

> 

> BTW, does anyone really run zswap on a RT system?


The bit spinlock is problematic for RT and needs a replacement. Having a
page not available in RT is a no no. But then it might be a good
testcase if mlock() has been setup properly :) But other than that, I
can't imagine a real use case.

I'm going to apply that patch for the time being.

Sebastian
diff mbox series

Patch

--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -82,7 +82,7 @@ 

 struct zsmalloc_handle {
 	unsigned long addr;
-	struct mutex lock;
+	spinlock_t lock;
 };

 #define ZS_HANDLE_ALLOC_SIZE (sizeof(struct zsmalloc_handle))
@@ -370,7 +370,7 @@  static unsigned long cache_alloc_handle(
 	if (p) {
 		struct zsmalloc_handle *zh = p;

-		mutex_init(&zh->lock);
+		spin_lock_init(&zh->lock);
 	}
 #endif
 	return (unsigned long)p;
@@ -927,7 +927,7 @@  static inline int testpin_tag(unsigned l
 #ifdef CONFIG_PREEMPT_RT
 	struct zsmalloc_handle *zh = zs_get_pure_handle(handle);

-	return mutex_is_locked(&zh->lock);
+	return spin_is_locked(&zh->lock);
 #else
 	return bit_spin_is_locked(HANDLE_PIN_BIT, (unsigned long *)handle);
 #endif
@@ -938,7 +938,7 @@  static inline int trypin_tag(unsigned lo
 #ifdef CONFIG_PREEMPT_RT
 	struct zsmalloc_handle *zh = zs_get_pure_handle(handle);

-	return mutex_trylock(&zh->lock);
+	return spin_trylock(&zh->lock);
 #else
 	return bit_spin_trylock(HANDLE_PIN_BIT, (unsigned long *)handle);
 #endif
@@ -949,7 +949,7 @@  static void pin_tag(unsigned long handle
 #ifdef CONFIG_PREEMPT_RT
 	struct zsmalloc_handle *zh = zs_get_pure_handle(handle);

-	return mutex_lock(&zh->lock);
+	return spin_lock(&zh->lock);
 #else
 	bit_spin_lock(HANDLE_PIN_BIT, (unsigned long *)handle);
 #endif
@@ -960,7 +960,7 @@  static void unpin_tag(unsigned long hand
 #ifdef CONFIG_PREEMPT_RT
 	struct zsmalloc_handle *zh = zs_get_pure_handle(handle);

-	return mutex_unlock(&zh->lock);
+	return spin_unlock(&zh->lock);
 #else
 	bit_spin_unlock(HANDLE_PIN_BIT, (unsigned long *)handle);
 #endif