lems; however, there are cases where different ports share the same resource, which lead to obscure timing related bugs such as the one fixed by commit 213373cf (ata_piix: fix locking around SIDPR access). This patch implements exclusion among EHs of the same host. When EH begins, it acquires per-host EH ownership by calling ata_eh_acquire(). When EH finishes, the ownership is released by calling ata_eh_release(). EH ownership is also released whenever the EH thread goes to sleep from ata_msleep() or explicitly and reacquired after waking up. This ensures that while EH is actively accessing the hardware, it has exclusive access to it while allowing EHs to interleave and progress in parallel as they hit waiting stages, which dominate the time spent in EH. This achieves cross-port EH exclusion without pervasive and fragile changes while still allowing parallel EH for the most part. This was first reported by yuanding02@gmail.com more than three years ago in the following bugzilla. :-) https://bugzilla.kernel.org/show_bug.cgi?id=8223 Signed-off-by: Tejun Heo Cc: Alan Cox Reported-by: yuanding02@gmail.com Signed-off-by: Jeff Garzik ¨ ÒWŸ%x