staging: sync: Fix a race condition between release_obj and print_obj

Before this change, a timeline would only be removed from the timeline
list *after* the sync driver had its release_obj() called. However, the
driver's release_obj() may free resources needed by print_obj().

Although the timeline list is locked when print_obj() is called, it is
not locked when release_obj() is called. If one CPU was in print_obj()
when another was in release_obj(), the print_obj() may make unsafe
accesses.

It is not actually necessary to hold the timeline list lock when calling
release_obj() if the call is made after the timeline is unlinked from
the list, since there is no possibility another thread could be in --
or enter -- print_obj() for that timeline.

This change moves the release_obj() call to after the timeline is
unlinked, preventing the above race from occurring.

Cc: Colin Cross <[email protected]>
Cc: Android Kernel Team <[email protected]>
Signed-off-by: Alistair Strachan <[email protected]>
[jstultz: minor commit subject tweak]
Signed-off-by: John Stultz <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

0 files changed, 0 insertions, 0 deletions