[Ocfs2-devel] [PATCH 1/1] ocfs2: use spinlock irqsave for downconvert lock.patch

[Srinivas Eeda]

When ocfs2dc thread holds dc_task_lock spinlock and receives soft IRQ for
I/O completion it deadlock itself trying to get same spinlock in
ocfs2_wake_downconvert_thread

The patch disables interrupts when acquiring dc_task_lock spinlock

Signed-off-by: Srinivas Eeda srinivas.e...@oracle.com
---
 fs/ocfs2/dlmglue.c |   30 ++
 1 files changed, 18 insertions(+), 12 deletions(-)

diff --git a/fs/ocfs2/dlmglue.c b/fs/ocfs2/dlmglue.c
index 81a4cd2..d8552a5 100644
--- a/fs/ocfs2/dlmglue.c
+++ b/fs/ocfs2/dlmglue.c
@@ -3932,6 +3932,8 @@ unqueue:
 static void ocfs2_schedule_blocked_lock(struct ocfs2_super *osb,
struct ocfs2_lock_res *lockres)
 {
+   unsigned long flags;
+
assert_spin_locked(lockres-l_lock);
 
if (lockres-l_flags  OCFS2_LOCK_FREEING) {
@@ -3945,21 +3947,22 @@ static void ocfs2_schedule_blocked_lock(struct 
ocfs2_super *osb,
 
lockres_or_flags(lockres, OCFS2_LOCK_QUEUED);
 
-   spin_lock(osb-dc_task_lock);
+   spin_lock_irqsave(osb-dc_task_lock, flags);
if (list_empty(lockres-l_blocked_list)) {
list_add_tail(lockres-l_blocked_list,
  osb-blocked_lock_list);
osb-blocked_lock_count++;
}
-   spin_unlock(osb-dc_task_lock);
+   spin_unlock_irqrestore(osb-dc_task_lock, flags);
 }
 
 static void ocfs2_downconvert_thread_do_work(struct ocfs2_super *osb)
 {
unsigned long processed;
+   unsigned long flags;
struct ocfs2_lock_res *lockres;
 
-   spin_lock(osb-dc_task_lock);
+   spin_lock_irqsave(osb-dc_task_lock, flags);
/* grab this early so we know to try again if a state change and
 * wake happens part-way through our work  */
osb-dc_work_sequence = osb-dc_wake_sequence;
@@ -3972,38 +3975,40 @@ static void ocfs2_downconvert_thread_do_work(struct 
ocfs2_super *osb)
 struct ocfs2_lock_res, l_blocked_list);
list_del_init(lockres-l_blocked_list);
osb-blocked_lock_count--;
-   spin_unlock(osb-dc_task_lock);
+   spin_unlock_irqrestore(osb-dc_task_lock, flags);
 
BUG_ON(!processed);
processed--;
 
ocfs2_process_blocked_lock(osb, lockres);
 
-   spin_lock(osb-dc_task_lock);
+   spin_lock_irqsave(osb-dc_task_lock, flags);
}
-   spin_unlock(osb-dc_task_lock);
+   spin_unlock_irqrestore(osb-dc_task_lock, flags);
 }
 
 static int ocfs2_downconvert_thread_lists_empty(struct ocfs2_super *osb)
 {
int empty = 0;
+   unsigned long flags;
 
-   spin_lock(osb-dc_task_lock);
+   spin_lock_irqsave(osb-dc_task_lock, flags);
if (list_empty(osb-blocked_lock_list))
empty = 1;
 
-   spin_unlock(osb-dc_task_lock);
+   spin_unlock_irqrestore(osb-dc_task_lock, flags);
return empty;
 }
 
 static int ocfs2_downconvert_thread_should_wake(struct ocfs2_super *osb)
 {
int should_wake = 0;
+   unsigned long flags;
 
-   spin_lock(osb-dc_task_lock);
+   spin_lock_irqsave(osb-dc_task_lock, flags);
if (osb-dc_work_sequence != osb-dc_wake_sequence)
should_wake = 1;
-   spin_unlock(osb-dc_task_lock);
+   spin_unlock_irqrestore(osb-dc_task_lock, flags);
 
return should_wake;
 }
@@ -4033,10 +4038,11 @@ static int ocfs2_downconvert_thread(void *arg)
 
 void ocfs2_wake_downconvert_thread(struct ocfs2_super *osb)
 {
-   spin_lock(osb-dc_task_lock);
+   unsigned long flags;
+   spin_lock_irqsave(osb-dc_task_lock, flags);
/* make sure the voting thread gets a swipe at whatever changes
 * the caller may have made to the voting state */
osb-dc_wake_sequence++;
-   spin_unlock(osb-dc_task_lock);
+   spin_unlock_irqrestore(osb-dc_task_lock, flags);
wake_up(osb-dc_event);
 }
-- 
1.5.4.3


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Re: [Ocfs2-devel] [PATCH 1/1] ocfs2: use spinlock irqsave for downconvert lock.patch

[Tao Ma]

Hi Srini,
On 01/29/2012 10:13 AM, Srinivas Eeda wrote:
 When ocfs2dc thread holds dc_task_lock spinlock and receives soft IRQ for
 I/O completion it deadlock itself trying to get same spinlock in
 ocfs2_wake_downconvert_thread
could you please describe it in more detail?

btw, if you are afraid of deadlocking in soft IRQ, I guess we should use
spin_lock_bh not spin_lock_irqsave?

Thanks
Tao
 
 The patch disables interrupts when acquiring dc_task_lock spinlock
 
 Signed-off-by: Srinivas Eeda srinivas.e...@oracle.com
 ---
  fs/ocfs2/dlmglue.c |   30 ++
  1 files changed, 18 insertions(+), 12 deletions(-)
 
 diff --git a/fs/ocfs2/dlmglue.c b/fs/ocfs2/dlmglue.c
 index 81a4cd2..d8552a5 100644
 --- a/fs/ocfs2/dlmglue.c
 +++ b/fs/ocfs2/dlmglue.c
 @@ -3932,6 +3932,8 @@ unqueue:
  static void ocfs2_schedule_blocked_lock(struct ocfs2_super *osb,
   struct ocfs2_lock_res *lockres)
  {
 + unsigned long flags;
 +
   assert_spin_locked(lockres-l_lock);
  
   if (lockres-l_flags  OCFS2_LOCK_FREEING) {
 @@ -3945,21 +3947,22 @@ static void ocfs2_schedule_blocked_lock(struct 
 ocfs2_super *osb,
  
   lockres_or_flags(lockres, OCFS2_LOCK_QUEUED);
  
 - spin_lock(osb-dc_task_lock);
 + spin_lock_irqsave(osb-dc_task_lock, flags);
   if (list_empty(lockres-l_blocked_list)) {
   list_add_tail(lockres-l_blocked_list,
 osb-blocked_lock_list);
   osb-blocked_lock_count++;
   }
 - spin_unlock(osb-dc_task_lock);
 + spin_unlock_irqrestore(osb-dc_task_lock, flags);
  }
  
  static void ocfs2_downconvert_thread_do_work(struct ocfs2_super *osb)
  {
   unsigned long processed;
 + unsigned long flags;
   struct ocfs2_lock_res *lockres;
  
 - spin_lock(osb-dc_task_lock);
 + spin_lock_irqsave(osb-dc_task_lock, flags);
   /* grab this early so we know to try again if a state change and
* wake happens part-way through our work  */
   osb-dc_work_sequence = osb-dc_wake_sequence;
 @@ -3972,38 +3975,40 @@ static void ocfs2_downconvert_thread_do_work(struct 
 ocfs2_super *osb)
struct ocfs2_lock_res, l_blocked_list);
   list_del_init(lockres-l_blocked_list);
   osb-blocked_lock_count--;
 - spin_unlock(osb-dc_task_lock);
 + spin_unlock_irqrestore(osb-dc_task_lock, flags);
  
   BUG_ON(!processed);
   processed--;
  
   ocfs2_process_blocked_lock(osb, lockres);
  
 - spin_lock(osb-dc_task_lock);
 + spin_lock_irqsave(osb-dc_task_lock, flags);
   }
 - spin_unlock(osb-dc_task_lock);
 + spin_unlock_irqrestore(osb-dc_task_lock, flags);
  }
  
  static int ocfs2_downconvert_thread_lists_empty(struct ocfs2_super *osb)
  {
   int empty = 0;
 + unsigned long flags;
  
 - spin_lock(osb-dc_task_lock);
 + spin_lock_irqsave(osb-dc_task_lock, flags);
   if (list_empty(osb-blocked_lock_list))
   empty = 1;
  
 - spin_unlock(osb-dc_task_lock);
 + spin_unlock_irqrestore(osb-dc_task_lock, flags);
   return empty;
  }
  
  static int ocfs2_downconvert_thread_should_wake(struct ocfs2_super *osb)
  {
   int should_wake = 0;
 + unsigned long flags;
  
 - spin_lock(osb-dc_task_lock);
 + spin_lock_irqsave(osb-dc_task_lock, flags);
   if (osb-dc_work_sequence != osb-dc_wake_sequence)
   should_wake = 1;
 - spin_unlock(osb-dc_task_lock);
 + spin_unlock_irqrestore(osb-dc_task_lock, flags);
  
   return should_wake;
  }
 @@ -4033,10 +4038,11 @@ static int ocfs2_downconvert_thread(void *arg)
  
  void ocfs2_wake_downconvert_thread(struct ocfs2_super *osb)
  {
 - spin_lock(osb-dc_task_lock);
 + unsigned long flags;
 + spin_lock_irqsave(osb-dc_task_lock, flags);
   /* make sure the voting thread gets a swipe at whatever changes
* the caller may have made to the voting state */
   osb-dc_wake_sequence++;
 - spin_unlock(osb-dc_task_lock);
 + spin_unlock_irqrestore(osb-dc_task_lock, flags);
   wake_up(osb-dc_event);
  }


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