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462b529f91
Kudos to Thibaut Varene for spotting the (mis)use of appropriately named global_ack_eiem. This took a long time to figure out and both insight from myself, Kyle McMartin, and James Bottomley were required to narrow down which bit of code could have this race condition. The symptom was interrupts stopped getting delivered while some workload was generating IO interrupts on two different CPUs. One of the interrupt sources would get masked off and stay unmasked. Problem was global_ack_eiem was accessed with read/modified/write sequence and not protected by a spinlock. PA-RISC doesn't need a global ack flag though. External Interrupts are _always_ delivered to a single CPU (except for "global broadcast interrupt" which AFAIK currently is not used.) So we don't have to worry about any given IRQ vector getting delivered to more than one CPU. Tested on a500 and rp34xx boxen. rsync to/from gsyprf11 (a500) would lock up the box since NIC (tg3) interrupt and SCSI (sym2) were on "opposite" CPUs (2 CPU system). Put them on the same CPU or apply this patch and 10GB of data would rsync completely. Please apply the following critical patch. thanks, grant Signed-off-by: Grant Grundler <grundler@parisc-linux.org> Acked-by: Thibaut VARENE <T-Bone@parisc-linux.org> Signed-off-by: Kyle McMartin <kyle@parisc-linux.org> |
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