Contribute/BiteSizedTasks

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Revision as of 15:51, 2 March 2016 by Eblake (talk | contribs) (→‎Tracing: Mention debug statement bitrot prevention)

API conversion

  • Look for uses of malloc, and convert them to either g_malloc, g_new (more rarely g_try_malloc or g_try_new if a lot of memory is being allocated). Likewise, convert calloc to either g_new0 or g_try_new0. Drop return value checks unless using g_try_new/g_try_new0.
  • Associate external libraries with the object files that actually use them
  • For all "QEMUTimer*" variables that are initialized with timer_new, change them to "QEMUTimer" and initialize them with timer_init. Drop any timer_free calls (there aren't many, so this patch would fix small memory leaks too). (not quite bite-sized).
  • Replace calls to functions named cpu_physical_memory_* with address_space_*.
  • Change net/socket.c to use the functions in include/qemu/sockets.h instead of parse_host_port/bind/connect/listen.
  • Change QemuMutex and QemuCond to CompatGMutex and CompatGCond (these are the same as GMutex and GCond, just with a different type). With this change, qemu_mutex_init/qemu_cond_init becomes optional for global variables.
  • Change get_ticks_per_sec() calls to just use the NANOSECONDS_PER_SECOND constant.
  • Remove macros IO_READ_PROTO and IO_WRITE_PROTO.
  • Replace calls to object_child_foreach() with object_child_foreach_recursive() when applicable.
  • Change basename and dirname to g_path_get_basename() and g_path_get_dirname() respectively.
  • Devices which create MemoryRegions with the old_mmio accessors should be converted to new style mmio accessors.

Header cleanups

  • avoid including include/exec/exec-all.h from other headers.
  • avoid including files from include/exec/cpu-common.h.

Device models

  • Include SDState by value instead of allocating it in sd_init (hw/sd/).
  • Look for invocations of qemu_system_reset_request() in hw/. Whenever they correspond to some kind of watchdog that has triggered, change to watchdog_perform_action().

Error checking

  • Add checks for NULL return value to uses of load_image_targphys, qemu_find_file.
  • Add checks for negative return value to uses of get_image_size, event_notifier_init, msix_init.
  • Use qemu_strtol/qemu_strtoul/qemu_strtoll/qemu_strtoull more.

Device lifecycle

  • IDE uses qemu_add_vm_change_state_handler() without a corresponding qemu_del_vm_change_state_handler(). This means hot unplugging an AHCI PCI adapter results in a dangling change state handler and could lead to a crash.

Dead code removal

  • hw/display contains files named *_template.h. These are included many times with different values of the DEPTH macro. However, only the DEPTH == 32 case is used. Remove support for DEPTH != 32 in the template headers and in the file that include them.
  • Look for functions that are named *_exit or *_exitfn in hw/ and that return int. They should all return zero. Make them return void, and remove the checks for the callers.
  • Once the above change is done, remove the "Error **" argument from functions named *_unrealize in hw/
  • Remove bdrv_aio_multiwrite() since virtio-blk no longer uses it and the only remaining caller, qemu-io, is for testing only

Tracing

  • Add tracepoints. All functions that are named something_helper, and all functions mentioned in MemoryRegionOps are good candidates.

Bitrot Prevention

  • Files with conditional debug statements should ensure that the printf is always compiled, and merely hidden behind if (0) when not debugging, rather than #ifdef'd out. This prevents bitrot of the format string of the debug statement. See commit c691320faa6 for an example. Or, go one step further and convert the debug statements to tracepoints.