This explanation is wrong. Please ignore those patches.
Sorry for confution.
On Thu, Aug 24, 2006 at 06:42:16PM +0900, Isaku Yamahata wrote:
__kernel_syscall_via_epc masks interrupt assuming page fault on the vDSO page
can't occur during executing.
However Xen might preempt vcpu when interrupt is disabled so that
page fault might occur with interrupt masked unlike baremetal case.
Such page fault results in acquiring semaphore with interrupt disabled.
see ia64_do_page_fault().
It means that we can't disable interrupt in vDSO page on xen environment.
So we jumps kernel text area which is pinned by ITR before disabling interrupt
to avoid such page fault.
thanks.
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yamahata
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