d28db80fd0
The behavior of RW_*_HELD was updated because it was not quite right. It is not sufficient to return non-zero when the lock is help, we must only do this when the current task in the holder. This means we need to track the lock owner which is not something tracked in a Linux semaphore. After some experimentation the solution I settled on was to embed the Linux semaphore at the start of a larger krwlock_t structure which includes the owner field. This maintains good performance and allows us to cleanly intergrate with the kernel lock analysis tools. My reasons: 1) By placing the Linux semaphore at the start of krwlock_t we can then simply cast krwlock_t to a rw_semaphore and pass that on to the linux kernel. This allows us to use '#defines so the preprocessor can do direct replacement of the Solaris primative with the linux equivilant. This is important because it then maintains the location information for each rw_* call point. 2) Additionally, by adding the owner to krwlock_t we can keep this needed extra information adjacent to the lock itself. This removes the need for a fancy lookup to get the owner which is optimal for performance. We can also leverage the existing spin lock in the semaphore to ensure owner is updated correctly. 3) All helper functions which do not need to strictly be implemented as a define to preserve location information can be done as a static inline function. 4) Adding the owner to krwlock_t allows us to remove all memory allocations done during lock initialization. This is good for all the obvious reasons, we do give up the ability to specific the lock name. The Linux profiling tools will stringify the lock name used in the code via the preprocessor and use that. Update rwlocks validated on: - SLES10 (ppc64) - SLES11 (x86_64) - CHAOS4.2 (x86_64) - RHEL5.3 (x86_64) - RHEL6 (x86_64) - FC11 (x86_64) |
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