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ac57fa9faf
Pull tracing fixes from Steven Rostedt: - Revert "tracing: Remove pid in task_rename tracing output" A change was made to remove the pid field from the task_rename event because it was thought that it was always done for the current task and recording the pid would be redundant. This turned out to be incorrect and there are a few corner case where this is not true and caused some regressions in tooling. - Fix the reading from user space for migration The reading of user space uses a seq lock type of logic where it uses a per-cpu temporary buffer and disables migration, then enables preemption, does the copy from user space, disables preemption, enables migration and checks if there was any schedule switches while preemption was enabled. If there was a context switch, then it is considered that the per-cpu buffer could be corrupted and it tries again. There's a protection check that tests if it takes a hundred tries, it issues a warning and exits out to prevent a live lock. This was triggered because the task was selected by the load balancer to be migrated to another CPU, every time preemption is enabled the migration task would schedule in try to migrate the task but can't because migration is disabled and let it run again. This caused the scheduler to schedule out the task every time it enabled preemption and made the loop never exit (until the 100 iteration test triggered). Fix this by enabling and disabling preemption and keeping migration enabled if the reading from user space needs to be done again. This will let the migration thread migrate the task and the copy from user space will likely pass on the next iteration. - Fix trace_marker copy option freeing The "copy_trace_marker" option allows a tracing instance to get a copy of a write to the trace_marker file of the top level instance. This is managed by a link list protected by RCU. When an instance is removed, a check is made if the option is set, and if so synchronized_rcu() is called. The problem is that an iteration is made to reset all the flags to what they were when the instance was created (to perform clean ups) was done before the check of the copy_trace_marker option and that option was cleared, so the synchronize_rcu() was never called. Move the clearing of all the flags after the check of copy_trace_marker to do synchronize_rcu() so that the option is still set if it was before and the synchronization is performed. - Fix entries setting when validating the persistent ring buffer When validating the persistent ring buffer on boot up, the number of events per sub-buffer is added to the sub-buffer meta page. The validator was updating cpu_buffer->head_page (the first sub-buffer of the per-cpu buffer) and not the "head_page" variable that was iterating the sub-buffers. This was causing the first sub-buffer to be assigned the entries for each sub-buffer and not the sub-buffer that was supposed to be updated. - Use "hash" value to update the direct callers When updating the ftrace direct callers, it assigned a temporary callback to all the callback functions of the ftrace ops and not just the functions represented by the passed in hash. This causes an unnecessary slow down of the functions of the ftrace_ops that is not being modified. Only update the functions that are going to be modified to call the ftrace loop function so that the update can be made on those functions. * tag 'trace-v7.0-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace: ftrace: Use hash argument for tmp_ops in update_ftrace_direct_mod ring-buffer: Fix to update per-subbuf entries of persistent ring buffer tracing: Fix trace_marker copy link list updates tracing: Fix failure to read user space from system call trace events tracing: Revert "tracing: Remove pid in task_rename tracing output"