On 02/27/2018 07:36 AM, Miroslav Benes wrote: > On Fri, 23 Feb 2018, Joe Lawrence wrote: > >> [ ... snip ... ] >> >> +If a livepatch is replaced by a cumulative patch, then only the >> +callbacks belonging to the cumulative patch will be executed. This >> +simplifies the livepatching core for it is the responsibility of the >> +cumulative patch to safely revert whatever needs to be reverted. See >> +Documentation/livepatch/cumulative.txt for more information on such >> +patches. > > s/cumulative/atomic replace/ almost everywhere? > > 'Documentation/livepatch/cumulative.txt' should be > 'Documentation/livepatch/cumulative-patches.txt' and we may rename it > atomic-replace-patches.txt. I don't know. Cumulative patches forms a > subset of atomic replace patches in my understanding. The feature itself > is more general. Even if practically used for cumulative patches only. But > it is for you and Petr to decide.
Hi Miroslav, Thanks for reviewing! I guess I'm a little confused about the distinction here. I understood a "cumulative-patch" to mean that it would contain the sum of all changes. So instead of this: patch 1 = A + patch 2 = B + patch 3 = C ----------------------- net = A + B + C We can group all of the changes together into a single cumulative-patch for the same net effect: patch 1 = A -replaced by- patch 2 = A + B -replaced by- patch 3 = A + B + C I assumed this would also mean to include any reverted changes as well. So in the example above, if change C needed to be reverted, then: patch 4 = A + B and that would still be considered a "cumulative-patch". In my mind, atomic replace is the mechanism that forces patching to be cumulative. Perhaps this is too strict? Are there other use-cases for atomic-replace? >> Example Use-cases >> ================= >> >> [ ... snip ... ] >> >> +Test 11 >> +------- >> + >> +A similar test as the previous one, except this time load the second >> +callback demo module as a cumulative (ie, replacement) patch. The >> +livepatching core will only execute klp_object callbacks for the latest >> +cumulative patch on the patch stack. >> + >> +- load livepatch >> +- load second livepatch (atomic replace) >> +- disable livepatch > > Not needed. Good catch. -- Joe
