diff options
Diffstat (limited to 'Documentation/PCI')
| -rw-r--r-- | Documentation/PCI/MSI-HOWTO.txt | 15 |
1 files changed, 3 insertions, 12 deletions
diff --git a/Documentation/PCI/MSI-HOWTO.txt b/Documentation/PCI/MSI-HOWTO.txt index 0d920d54536d..63def8ef546d 100644 --- a/Documentation/PCI/MSI-HOWTO.txt +++ b/Documentation/PCI/MSI-HOWTO.txt @@ -501,18 +501,9 @@ necessary to disable interrupts (Linux guarantees the same interrupt will not be re-entered). If a device uses multiple interrupts, the driver must disable interrupts while the lock is held. If the device sends a different interrupt, the driver will deadlock trying to recursively -acquire the spinlock. - -There are two solutions. The first is to take the lock with -spin_lock_irqsave() or spin_lock_irq() (see -Documentation/DocBook/kernel-locking). The second is to specify -IRQF_DISABLED to request_irq() so that the kernel runs the entire -interrupt routine with interrupts disabled. - -If your MSI interrupt routine does not hold the lock for the whole time -it is running, the first solution may be best. The second solution is -normally preferred as it avoids making two transitions from interrupt -disabled to enabled and back again. +acquire the spinlock. Such deadlocks can be avoided by using +spin_lock_irqsave() or spin_lock_irq() which disable local interrupts +and acquire the lock (see Documentation/DocBook/kernel-locking). 4.6 How to tell whether MSI/MSI-X is enabled on a device |