xen: only enable interrupts while actually blocking for spinlock

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Where possible we enable interrupts while waiting for a spinlock to
become free, in order to reduce big latency spikes in interrupt handling.

However, at present if we manage to pick up the spinlock just before
blocking, we'll end up holding the lock with interrupts enabled for a
while.  This will cause a deadlock if we recieve an interrupt in that
window, and the interrupt handler tries to take the lock too.

Solve this by shrinking the interrupt-enabled region to just around the
blocking call.

[ Impact: avoid race/deadlock when using Xen PV spinlocks ]

Reported-by: "Yang, Xiaowei" <xiaowei.yang@intel.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

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This commit is contained in:

Jeremy Fitzhardinge 2009-09-09 12:33:51 -07:00

parent 577eebeae3

commit 4d576b57b5

1 changed files with 11 additions and 8 deletions

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arch/x86/xen/spinlock.c

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