[PATCH] RCU idle detection fix
Patch from Dipankar Sarma <dipankar@in.ibm.com> There is a check in RCU for idle CPUs which signifies quiescent state (and hence no reference to RCU protected data) which was broken when interrupt counters were changed to use thread_info->preempt_count. Martin's 32 CPU machine with many idle CPUs was not completing any RCU grace period because RCU was forever waiting for idle CPUs to context switch. Had the idle check worked, this would not have happened. With no RCU happening, the dentries were getting "freed" (dentry stats showing that) but not getting returned to slab. This would not show up in systems that are generally busy as context switches then would happen in all CPUs and the per-CPU quiescent state counter would get incremented during context switch.
Showing
Please register or sign in to comment