Brent Casavant e08e6c5213 [IA64] hooks to wait for mmio writes to drain when migrating processes ... On SN2, MMIO writes which are issued from separate processors are not guaranteed to arrive in any particular order at the IO hardware. When performing such writes from the kernel this is not a problem, as a kernel thread will not migrate to another CPU during execution, and mmiowb() calls can guarantee write ordering when control of the IO resource is allowed to move between threads. However, when MMIO writes can be performed from user space (e.g. DRM) there are no such guarantees and mechanisms, as the process may context-switch at any time, and may migrate to a different CPU as part of the switch. For such programs/hardware to operate correctly, it is required that the MMIO writes from the old CPU be accepted by the IO hardware before subsequent writes from the new CPU can be issued. The following patch implements this behavior on SN2 by waiting for a Shub register to indicate that these writes have been accepted. This is placed in the context switch-in path, and only performs the wait when the newly scheduled task changes CPUs. Signed-off-by: Prarit Bhargava <prarit@sgi.com> Signed-off-by: Brent Casavant <bcasavan@sgi.com>		2006-01-26 15:55:52 -08:00
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kernel	[IA64] hooks to wait for mmio writes to drain when migrating processes	2006-01-26 15:55:52 -08:00
pci	[IA64-SGI] pass segment# on SN_SAL_IOIF_SLOT_{DIS,EN}ABLE calls	2006-01-17 10:22:46 -08:00
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