Messages in this thread | | | Date | Mon, 11 May 2009 17:21:42 +0530 | From | "K.Prasad" <> | Subject | [Patch 00/12] Hardware Breakpoint interfaces |
| |
Hi Alan, Please find the new set of patches with the changes mentioned below. Kindly let me know your comments with respect to the same.
Hi Frederic/Steven, Please find a few changes in the ftrace plugin code w.r.t. synchronisation primitives (prefixed in the changelog with FTRACE). Kindly let me know your comments.
Changelog -----------
- on_each_cpu() call will now return only after all functions calls made through IPI have finished (@wait parameter is set to 1). This is required since changes made in code following on_each_cpu() [such as incrementing hbp_kernel_pos] have side-effects on the execution of the functions invoked through IPIs. It is also safe to make them wait inside spin_lock() context as it does a busy wait using cpu_relax().
- Introduced a new per-cpu array of pointers to 'struct hw_breakpoint' called 'this_hbp_kernel'. This per-cpu variable helps overcome any side-effects in hbp_handler() due to parallel execution of (un)register_kernel_hw_breakpoint() on other CPUs causing 'hbp_kernel' value to change.
- Hardware Breakpoint exceptions due to lazy debug register switching is now identified through the absence of TIF_DEBUG task flag in the current process. This eliminates the need to store the process that last set the debug register in 'last_debugged_task'.
- Converted spin_lock() in kernel/hw_breakpoint.c to spin_lock_bh(). This is to ward-off potential circular dependancy over 'hw_breakpoint_lock' when flush_thread_hw_breakpoint() is invoked in softIRQ context.
- Ptrace code now directly uses the exported interfaces (un)register_user_hw_breakpoint() thereby addressing some of the issues pointed out in code-review here:http://lkml.org/lkml/2009/5/4/367.
- An optimisation in arch_update_kernel_hw_breakpoints() code resulting in a few modifications to the function and removal of kdr7_masks[] global array (as pointed out by Alan Stern).
- [FTRACE] Implementation of RCU based locking mechanism in the ftrace plugin code (kernel/trace/trace_ksym.c), specially to avoid the potential circular dependancy through ksym_collect_stats() invoked in exception context (while attempting to acquite a spin_lock() already used in control-plane). All add/delete operations to the hlist pointed by 'ksym_filter_head' are now protected by RCU.
- [FTRACE] Revert the spin_lock() based implementation in kernel/trace/trace_ksym.c to mutex based one, as a result of the above change. These locks are no longer required in preempt_disable() code due to RCU implementation in ksym_collect_stats() and hence the change.
- The patches are now based on commit 5863f0756c57cc0ce23701138bfc88ab3d1f3721 of -tip tree.
Thanks, K.Prasad
| |