| Message ID | d5f8364b42f277daa9e235d23398e3dce5549e92.1724324945.git.petrm@nvidia.com (mailing list archive) |
|---|---|
| State | RFC |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | selftests: forwarding: Introduce deferred commands | expand |
On Thu, Aug 22, 2024 at 03:49:40PM +0200, Petr Machata wrote: > In commit 8510801a9dbd ("selftests: drv-net: add ability to schedule > cleanup with defer()"), a defer helper was added to Python selftests. > The idea is to keep cleanup commands close to their dirtying counterparts, > thereby making it more transparent what is cleaning up what, making it > harder to miss a cleanup, and make the whole cleanup business exception > safe. All these benefits are applicable to bash as well, exception safety > can be interpreted in terms of safety vs. a SIGINT. > > This patch therefore introduces a framework of several helpers that serve > to schedule cleanups in bash selftests: > > - defer_scope_push(), defer_scope_pop(): Deferred statements can be batched > together in scopes. When a scope is popped, the deferred commands > schoduled in that scope are executed in the order opposite to order of s/schoduled/scheduled/ > their scheduling. > > - defer(): Schedules a defer to the most recently pushed scope (or the > default scope if none was pushed.) > > - defer_scopes_cleanup(): Pops any unpopped scopes, including the default > one. The selftests that use defer should run this in their cleanup > function. This is important to get cleanups of interrupted scripts. > > Consistent use of defers however obviates the need for a separate cleanup > function -- everything is just taken care of in defers. So this patch > actually introduces a cleanup() helper in the forwarding lib.sh, which > calls just pre_cleanup() and defer_scopes_cleanup(). Selftests are > obviously still free to override the function. > > - defer_scoped_fn(): Sometimes a function would like to introduce a new > defer scope, then run whatever it is that it wants to run, and then pop > the scope to run the deferred cleanups. The helper defer_scoped_fn() can > be used to derive from one function its wrapper that pushes a defer scope > before the function is called, and pops it after it returns. > > The following patches will convert several selftests to this new framework. The intention is to make sure new tests are using these helpers? > > Signed-off-by: Petr Machata <petrm@nvidia.com> > --- > tools/testing/selftests/net/forwarding/lib.sh | 83 +++++++++++++++++++ Does it make sense to place these helpers in net/lib.sh?
On 8/22/24 15:49, Petr Machata wrote: > In commit 8510801a9dbd ("selftests: drv-net: add ability to schedule > cleanup with defer()"), a defer helper was added to Python selftests. > The idea is to keep cleanup commands close to their dirtying counterparts, > thereby making it more transparent what is cleaning up what, making it > harder to miss a cleanup, and make the whole cleanup business exception > safe. All these benefits are applicable to bash as well, exception safety > can be interpreted in terms of safety vs. a SIGINT. > > This patch therefore introduces a framework of several helpers that serve > to schedule cleanups in bash selftests: Thank you for working on that, it would be great to have such improvement for bash scripts in general, not limited to kselftests! > tools/testing/selftests/net/forwarding/lib.sh | 83 +++++++++++++++++++ Make it a new file in more generic location, add a comment section with some examples and write down any assumptions there, perhaps defer.sh? > - defer_scope_push(), defer_scope_pop(): Deferred statements can be batched > together in scopes. When a scope is popped, the deferred commands > schoduled in that scope are executed in the order opposite to order of > their scheduling. tldr of this sub-comment at the end such API could be used in two variants: 1) function test_executor1() { for t in tests; do defer_scope_push() exec_test1 $t defer_scope_pop() done } 2) function test_executor2() { for t in tests; do exec_test2 $t done } function exec_test2() { defer_scope_push() do_stuff "$@" defer_scope_pop() } That fractals down in the same way for "subtests", or some special stuff like "make a zip" sub/task that will be used. And it could be misused as a mix of the two variants. I believe that the 1) is the better way, rationale: you write normal code that does what needs to be done, using defer(), and caller (that knows better) decides whether to sub-scope. As this defer is very similar to golang's in intention, I would give yet another analogy from golang's world. It's similar to concurrency, you write normal code that could be parallelized via "go" keyword, instead of writing async code that needs to be awaited for. Going back to the use case variants, there is no much sense to have push() and pop() dispersed by much from each other, thus I would like to introduce an API that just combines the two instead: new_scope exec_test1 $t (name discussion below) > > - defer(): Schedules a defer to the most recently pushed scope (or the > default scope if none was pushed. > > - defer_scopes_cleanup(): Pops any unpopped scopes, including the default > one. The selftests that use defer should run this in their cleanup > function. This is important to get cleanups of interrupted scripts. this should be *the* trap(1) with that said, it should be internal to the defer.sh script and it should be obvious that developers must not introduce their own trap (as of now we have ~330 in kselftests, ~270 of which in networking) > > Consistent use of defers however obviates the need for a separate cleanup > function -- everything is just taken care of in defers. So this patch > actually introduces a cleanup() helper in the forwarding lib.sh, which > calls just pre_cleanup() and defer_scopes_cleanup(). Selftests are > obviously still free to override the function. > > - defer_scoped_fn(): Sometimes a function would like to introduce a new > defer scope, then run whatever it is that it wants to run, and then pop > the scope to run the deferred cleanups. The helper defer_scoped_fn() can > be used to derive from one function its wrapper that pushes a defer scope > before the function is called, and pops it after it returns. It is basically a helper I would like to see as new_scope() mentioned above, but it takes it upside down - it should really be the caller that sub-scopes. I think that the name of the new_scope() would be better, still concise, but more precise as: subscope_defer(), trapped(), or sub_trap(). I have no idea how to make a sub-trapped, SIGSEGV isolated scope of bash execution that has ability to still edit outer scope variables. Perhaps we could relax the need for edit to have easier implementation? It is "all ok or failure/rollback" mode of operation anyway most of the time. After the above parts will be discussed out I will look more into the details of the code more deeply.
Ido Schimmel <idosch@nvidia.com> writes: > On Thu, Aug 22, 2024 at 03:49:40PM +0200, Petr Machata wrote: >> The following patches will convert several selftests to this new framework. > > The intention is to make sure new tests are using these helpers? Well, I sent this as RFC because I'm not sure how far to push it. I think it would be ideal if this were adopted, because then cleanups either always work, or are always broken, and we don't get partial or forgotten cleanups. That's for new tests, I do not foresee converting the existing selftests beyond a couple examples. >> >> Signed-off-by: Petr Machata <petrm@nvidia.com> >> --- >> tools/testing/selftests/net/forwarding/lib.sh | 83 +++++++++++++++++++ > > Does it make sense to place these helpers in net/lib.sh? Yeah, it does.
Przemek Kitszel <przemyslaw.kitszel@intel.com> writes: > On 8/22/24 15:49, Petr Machata wrote: >> In commit 8510801a9dbd ("selftests: drv-net: add ability to schedule >> cleanup with defer()"), a defer helper was added to Python selftests. >> The idea is to keep cleanup commands close to their dirtying counterparts, >> thereby making it more transparent what is cleaning up what, making it >> harder to miss a cleanup, and make the whole cleanup business exception >> safe. All these benefits are applicable to bash as well, exception safety >> can be interpreted in terms of safety vs. a SIGINT. >> This patch therefore introduces a framework of several helpers that serve >> to schedule cleanups in bash selftests: > > Thank you for working on that, it would be great to have such > improvement for bash scripts in general, not limited to kselftests! > >> tools/testing/selftests/net/forwarding/lib.sh | 83 +++++++++++++++++++ > > Make it a new file in more generic location, add a comment section with > some examples and write down any assumptions there, perhaps defer.sh? I can do it, but it's gonna be more pain in setting up those TEST_INCLUDES. People will forget. It will be a nuisance. I'm thinking of just moving it to net/lib.sh, from forwarding. >> - defer_scope_push(), defer_scope_pop(): Deferred statements can be batched > together in scopes. >> When a scope is popped, the deferred commands >> schoduled in that scope are executed in the order opposite to order of >> their scheduling. > > tldr of this sub-comment at the end > > such API could be used in two variants: > > 1) > function test_executor1() { > for t in tests; do > defer_scope_push() > exec_test1 $t > defer_scope_pop() > done > } > > 2) > function test_executor2() { > for t in tests; do > exec_test2 $t > done > } > function exec_test2() { > defer_scope_push() > do_stuff "$@" > defer_scope_pop() > } > > That fractals down in the same way for "subtests", or some special stuff > like "make a zip" sub/task that will be used. And it could be misused as > a mix of the two variants. > I believe that the 1) is the better way, rationale: you write normal > code that does what needs to be done, using defer(), and caller (that > knows better) decides whether to sub-scope. But the caller does not know better. The cleanups can't be done "sometime", but at a predictable place, so that they don't end up interfering with other work. The callee knows where it needs the cleanups to happen. The caller shouldn't have to know. > As this defer is very similar to golang's in intention, I would give > yet another analogy from golang's world. It's similar to concurrency, you write normal code that > could be parallelized via "go" keyword, > instead of writing async code that needs to be awaited for. Notice how in go, defer also runs at function exit. Similarly with C++ destructors, run on scope exit. There's no caller-defined "collection point". Putting off until "sometime" works for memory. Things like garbage collection, obstacks, autorelease pools, etc. work, because there's plenty of memory and we don't mind keeping stuff around until later. But that doesn't work for the sort of cleanups that selftests typically need to do. > Going back to the use case variants, there is no much sense to have > push() and pop() dispersed by much from each other, thus I would like > to introduce an API that just combines the two instead: > > new_scope exec_test1 $t > (name discussion below) > >> - defer(): Schedules a defer to the most recently pushed scope (or the >> default scope if none was pushed. > >> - defer_scopes_cleanup(): Pops any unpopped scopes, including the default >> one. The selftests that use defer should run this in their cleanup >> function. This is important to get cleanups of interrupted scripts. > > this should be *the* trap(1) > > with that said, it should be internal to the defer.sh script and it > should be obvious that developers must not introduce their own trap > (as of now we have ~330 in kselftests, ~270 of which in networking) Yeah, we have 100+ tests that use their own traps in forwarding alone. That ship has sailed. I agree that the defer module probably has the "right" to own the exit trap. Any other cleanups can be expressed in terms of defer, and I don't know if there are legitimate uses of exit trap with that taken out. But that's for sometime. >> Consistent use of defers however obviates the need for a separate cleanup >> function -- everything is just taken care of in defers. So this patch >> actually introduces a cleanup() helper in the forwarding lib.sh, which >> calls just pre_cleanup() and defer_scopes_cleanup(). Selftests are >> obviously still free to override the function. >> - defer_scoped_fn(): Sometimes a function would like to introduce a new >> defer scope, then run whatever it is that it wants to run, and then pop >> the scope to run the deferred cleanups. The helper defer_scoped_fn() can >> be used to derive from one function its wrapper that pushes a defer scope >> before the function is called, and pops it after it returns. > > It is basically a helper I would like to see as new_scope() mentioned > above, but it takes it upside down - it should really be the caller that > sub-scopes. > > I think that the name of the new_scope() would be better, still concise, > but more precise as: > subscope_defer(), > trapped(), or > sub_trap(). > > I have no idea how to make a sub-trapped, SIGSEGV isolated scope of bash > execution that has ability to still edit outer scope variables. Perhaps > we could relax the need for edit to have easier implementation? It is > "all ok or failure/rollback" mode of operation anyway most of the time. I'm not sure what you have in mind. > After the above parts will be discussed out I will look more into the > details of the code more deeply.
On Mon, 26 Aug 2024 16:25:47 +0200 Petr Machata wrote: > >> tools/testing/selftests/net/forwarding/lib.sh | 83 +++++++++++++++++++ > > > > Does it make sense to place these helpers in net/lib.sh? > > Yeah, it does. Would it further make sense to split them to their own file (net/lib_defer.sh?) and source that in net/lib.sh? Should be pretty self-contained.
On Mon, 26 Aug 2024 13:03:43 -0700 Jakub Kicinski wrote: > > > Does it make sense to place these helpers in net/lib.sh? > > > > Yeah, it does. > > Would it further make sense to split them to their own file > (net/lib_defer.sh?) and source that in net/lib.sh? > > Should be pretty self-contained. Just saw your reply to Przemek, makes sense.
On 8/26/24 17:20, Petr Machata wrote: > > Przemek Kitszel <przemyslaw.kitszel@intel.com> writes: > >> On 8/22/24 15:49, Petr Machata wrote: >>> In commit 8510801a9dbd ("selftests: drv-net: add ability to schedule >>> cleanup with defer()"), a defer helper was added to Python selftests. >>> The idea is to keep cleanup commands close to their dirtying counterparts, >>> thereby making it more transparent what is cleaning up what, making it >>> harder to miss a cleanup, and make the whole cleanup business exception >>> safe. All these benefits are applicable to bash as well, exception safety >>> can be interpreted in terms of safety vs. a SIGINT. >>> This patch therefore introduces a framework of several helpers that serve >>> to schedule cleanups in bash selftests: >> >> Thank you for working on that, it would be great to have such >> improvement for bash scripts in general, not limited to kselftests! >> >>> tools/testing/selftests/net/forwarding/lib.sh | 83 +++++++++++++++++++ >> >> Make it a new file in more generic location, add a comment section with >> some examples and write down any assumptions there, perhaps defer.sh? > > I can do it, but it's gonna be more pain in setting up those > TEST_INCLUDES. People will forget. It will be a nuisance. > > I'm thinking of just moving it to net/lib.sh, from forwarding. what about separate file, but included from net/lib.sh? > >>> - defer_scope_push(), defer_scope_pop(): Deferred statements can be batched > together in scopes. >>> When a scope is popped, the deferred commands >>> schoduled in that scope are executed in the order opposite to order of >>> their scheduling. >> >> tldr of this sub-comment at the end >> >> such API could be used in two variants: >> >> 1) >> function test_executor1() { >> for t in tests; do >> defer_scope_push() >> exec_test1 $t >> defer_scope_pop() >> done >> } >> >> 2) >> function test_executor2() { >> for t in tests; do >> exec_test2 $t >> done >> } >> function exec_test2() { >> defer_scope_push() >> do_stuff "$@" >> defer_scope_pop() >> } >> >> That fractals down in the same way for "subtests", or some special stuff >> like "make a zip" sub/task that will be used. And it could be misused as >> a mix of the two variants. >> I believe that the 1) is the better way, rationale: you write normal >> code that does what needs to be done, using defer(), and caller (that >> knows better) decides whether to sub-scope. > > But the caller does not know better. The cleanups can't be done > "sometime", but at a predictable place, so that they don't end up > interfering with other work. The callee knows where it needs the > cleanups to happen. The caller shouldn't have to know. The caller should not have to know what will be cleaned, but knows that they are done with callee. OTOH, callee has no idea about the "other work". > >> As this defer is very similar to golang's in intention, I would give >> yet another analogy from golang's world. It's similar to concurrency, you write normal code that >> could be parallelized via "go" keyword, >> instead of writing async code that needs to be awaited for. > > Notice how in go, defer also runs at function exit. Similarly with C++ > destructors, run on scope exit. There's no caller-defined "collection > point". > > Putting off until "sometime" works for memory. Things like garbage > collection, obstacks, autorelease pools, etc. work, because there's > plenty of memory and we don't mind keeping stuff around until later. But > that doesn't work for the sort of cleanups that selftests typically need > to do. That's true. But I still believe that it's the caller (or better, "glue code") responsibility to take care of cleanup schedule. > >> Going back to the use case variants, there is no much sense to have >> push() and pop() dispersed by much from each other, thus I would like >> to introduce an API that just combines the two instead: >> >> new_scope exec_test1 $t >> (name discussion below) >> >>> - defer(): Schedules a defer to the most recently pushed scope (or the >>> default scope if none was pushed. > >>> - defer_scopes_cleanup(): Pops any unpopped scopes, including the default >>> one. The selftests that use defer should run this in their cleanup >>> function. This is important to get cleanups of interrupted scripts. >> >> this should be *the* trap(1) >> >> with that said, it should be internal to the defer.sh script and it >> should be obvious that developers must not introduce their own trap >> (as of now we have ~330 in kselftests, ~270 of which in networking) > > Yeah, we have 100+ tests that use their own traps in forwarding alone. > That ship has sailed. > > I agree that the defer module probably has the "right" to own the exit > trap. Any other cleanups can be expressed in terms of defer, and I don't > know if there are legitimate uses of exit trap with that taken out. But > that's for sometime. There could be multiple traps for ERR/EXIT/etc conditions, but for simplicity it's best to rely on just EXIT trap. So we should convert current scripts one by one to use your new API. > >>> Consistent use of defers however obviates the need for a separate cleanup >>> function -- everything is just taken care of in defers. So this patch >>> actually introduces a cleanup() helper in the forwarding lib.sh, which >>> calls just pre_cleanup() and defer_scopes_cleanup(). Selftests are >>> obviously still free to override the function. >>> - defer_scoped_fn(): Sometimes a function would like to introduce a new >>> defer scope, then run whatever it is that it wants to run, and then pop >>> the scope to run the deferred cleanups. The helper defer_scoped_fn() can >>> be used to derive from one function its wrapper that pushes a defer scope >>> before the function is called, and pops it after it returns. >> >> It is basically a helper I would like to see as new_scope() mentioned >> above, but it takes it upside down - it should really be the caller that >> sub-scopes. >> >> I think that the name of the new_scope() would be better, still concise, >> but more precise as: >> subscope_defer(), >> trapped(), or >> sub_trap(). here I mean that "scope" is too broad without the word "trap" or "defer" in name >> >> I have no idea how to make a sub-trapped, SIGSEGV isolated scope of bash >> execution that has ability to still edit outer scope variables. Perhaps >> we could relax the need for edit to have easier implementation? It is >> "all ok or failure/rollback" mode of operation anyway most of the time. > > I'm not sure what you have in mind. foo=1 function bumpfoo { maybe-crash foo=2 } new-defer-scope bumpfoo echo $foo do you want this to print 2 or 1? > >> After the above parts will be discussed out I will look more into the >> details of the code more deeply. >
Przemek Kitszel <przemyslaw.kitszel@intel.com> writes: > On 8/26/24 17:20, Petr Machata wrote: >> Przemek Kitszel <przemyslaw.kitszel@intel.com> writes: >> >>> On 8/22/24 15:49, Petr Machata wrote: >>>> In commit 8510801a9dbd ("selftests: drv-net: add ability to schedule >>>> cleanup with defer()"), a defer helper was added to Python selftests. >>>> The idea is to keep cleanup commands close to their dirtying counterparts, >>>> thereby making it more transparent what is cleaning up what, making it >>>> harder to miss a cleanup, and make the whole cleanup business exception >>>> safe. All these benefits are applicable to bash as well, exception safety >>>> can be interpreted in terms of safety vs. a SIGINT. >>>> This patch therefore introduces a framework of several helpers that serve >>>> to schedule cleanups in bash selftests: >>> >>> Thank you for working on that, it would be great to have such >>> improvement for bash scripts in general, not limited to kselftests! >>> >>>> tools/testing/selftests/net/forwarding/lib.sh | 83 +++++++++++++++++++ >>> >>> Make it a new file in more generic location, add a comment section with >>> some examples and write down any assumptions there, perhaps defer.sh? >> I can do it, but it's gonna be more pain in setting up those >> TEST_INCLUDES. People will forget. It will be a nuisance. >> I'm thinking of just moving it to net/lib.sh, from forwarding. > > what about separate file, but included from net/lib.sh? Unfortunately that would be even worse. Then you need to remember to put the file into TEST_INCLUDES despite seemingly not using it. Like ideally we'd have automation for this. But I don't know how to do that without actually parsing the bash files, and that's just asking for trouble. Maybe after the defer stuff we also need a module system :-/ >>>> - defer_scope_push(), defer_scope_pop(): Deferred statements can be batched > together in scopes. >>>> When a scope is popped, the deferred commands >>>> schoduled in that scope are executed in the order opposite to order of >>>> their scheduling. >>> >>> tldr of this sub-comment at the end >>> >>> such API could be used in two variants: >>> >>> 1) >>> function test_executor1() { >>> for t in tests; do >>> defer_scope_push() >>> exec_test1 $t >>> defer_scope_pop() >>> done >>> } >>> >>> 2) >>> function test_executor2() { >>> for t in tests; do >>> exec_test2 $t >>> done >>> } >>> function exec_test2() { >>> defer_scope_push() >>> do_stuff "$@" >>> defer_scope_pop() >>> } >>> >>> That fractals down in the same way for "subtests", or some special stuff >>> like "make a zip" sub/task that will be used. And it could be misused as >>> a mix of the two variants. >>> I believe that the 1) is the better way, rationale: you write normal >>> code that does what needs to be done, using defer(), and caller (that >>> knows better) decides whether to sub-scope. >> But the caller does not know better. The cleanups can't be done >> "sometime", but at a predictable place, so that they don't end up >> interfering with other work. The callee knows where it needs the >> cleanups to happen. The caller shouldn't have to know. > > The caller should not have to know what will be cleaned, but knows that > they are done with callee. > > OTOH, callee has no idea about the "other work". Nor should it have to. It just needs to dispose of all responsibilities it has acquired (read: clean up what it has dirtied, or what others have dirtied for it). That's done by closing the defer scope. But let me take a step back. I've been going back and forth on this basically since yesterday. In practice, the caller-defined scopes lead to nicer code. If run_tests creates an implicit scope per test, most of the tests can just issue their defers without thinking about it too much. For cases where the implicit scope is not enough, the caller has to know that a certain function needs to be run in a dedicated scope or else it will interfere with something else that it's running. That's not great, it complicates the caller-callee contract in a way that's not captured anywhere in the syntax. But I suspect it's going to be just fine, these scripts are not exactly complex, and if there's an interference, I figure it will be easy to notice. The major upside is that we avoid the need to pepper the code with defer_scoped_fn. So I'll drop defer_scoped_fn and add in_defer_scope: in_defer_scope() { local ret defer_scope_push "$@" ret=$? defer_scope_pop return ret } >>> Going back to the use case variants, there is no much sense to have >>> push() and pop() dispersed by much from each other, thus I would like >>> to introduce an API that just combines the two instead: >>> >>> new_scope exec_test1 $t >>> (name discussion below) >>> >>>> - defer(): Schedules a defer to the most recently pushed scope (or the >>>> default scope if none was pushed. > >>>> - defer_scopes_cleanup(): Pops any unpopped scopes, including the default >>>> one. The selftests that use defer should run this in their cleanup >>>> function. This is important to get cleanups of interrupted scripts. >>> >>> this should be *the* trap(1) >>> >>> with that said, it should be internal to the defer.sh script and it >>> should be obvious that developers must not introduce their own trap >>> (as of now we have ~330 in kselftests, ~270 of which in networking) >> Yeah, we have 100+ tests that use their own traps in forwarding alone. >> That ship has sailed. >> I agree that the defer module probably has the "right" to own the exit >> trap. Any other cleanups can be expressed in terms of defer, and I don't >> know if there are legitimate uses of exit trap with that taken out. But >> that's for sometime. > > There could be multiple traps for ERR/EXIT/etc conditions, but for > simplicity it's best to rely on just EXIT trap. > So we should convert current scripts one by one to use your new API. I'd just grandfather those in, but having this stuff consolidated would obviously be nice. I think in practice we just need to add the trap registration to forwarding.sh, and per bash script do something like: -trap cleanup EXIT setup_prepare +defer cleanup setup_wait It should be fairly mechanical most of the time. But the defer stuff works without it as well, so we can take care of that later on. >>>> Consistent use of defers however obviates the need for a separate cleanup >>>> function -- everything is just taken care of in defers. So this patch >>>> actually introduces a cleanup() helper in the forwarding lib.sh, which >>>> calls just pre_cleanup() and defer_scopes_cleanup(). Selftests are >>>> obviously still free to override the function. >>>> - defer_scoped_fn(): Sometimes a function would like to introduce a new >>>> defer scope, then run whatever it is that it wants to run, and then pop >>>> the scope to run the deferred cleanups. The helper defer_scoped_fn() can >>>> be used to derive from one function its wrapper that pushes a defer scope >>>> before the function is called, and pops it after it returns. >>> >>> It is basically a helper I would like to see as new_scope() mentioned >>> above, but it takes it upside down - it should really be the caller that >>> sub-scopes. >>> >>> I think that the name of the new_scope() would be better, still concise, >>> but more precise as: >>> subscope_defer(), >>> trapped(), or >>> sub_trap(). > > here I mean that "scope" is too broad without the word "trap" or "defer" > in name > >>> >>> I have no idea how to make a sub-trapped, SIGSEGV isolated scope of bash >>> execution that has ability to still edit outer scope variables. Perhaps >>> we could relax the need for edit to have easier implementation? It is >>> "all ok or failure/rollback" mode of operation anyway most of the time. >> I'm not sure what you have in mind. > > foo=1 > function bumpfoo { > maybe-crash > foo=2 > } > new-defer-scope bumpfoo > echo $foo > > do you want this to print 2 or 1? Oh, that's what you mean by relaxing the edits. Yeah, I think I'd want that to print 2 if at all possible. I think in_ns() is the only helper that violates this.
On Tue, 27 Aug 2024 10:53:53 +0200 Petr Machata wrote: > >> I can do it, but it's gonna be more pain in setting up those > >> TEST_INCLUDES. People will forget. It will be a nuisance. > >> I'm thinking of just moving it to net/lib.sh, from forwarding. > > > > what about separate file, but included from net/lib.sh? > > Unfortunately that would be even worse. Then you need to remember to put > the file into TEST_INCLUDES despite seemingly not using it. > > Like ideally we'd have automation for this. But I don't know how to do that > without actually parsing the bash files, and that's just asking for > trouble. Maybe after the defer stuff we also need a module system :-/ FWIW we could throw it into net/lib, which has a fake target, see: b86761ff6374 ("selftests: net: add scaffolding for Netlink tests in Python")
Jakub Kicinski <kuba@kernel.org> writes: > On Tue, 27 Aug 2024 10:53:53 +0200 Petr Machata wrote: >> >> I can do it, but it's gonna be more pain in setting up those >> >> TEST_INCLUDES. People will forget. It will be a nuisance. >> >> I'm thinking of just moving it to net/lib.sh, from forwarding. >> > >> > what about separate file, but included from net/lib.sh? >> >> Unfortunately that would be even worse. Then you need to remember to put >> the file into TEST_INCLUDES despite seemingly not using it. >> >> Like ideally we'd have automation for this. But I don't know how to do that >> without actually parsing the bash files, and that's just asking for >> trouble. Maybe after the defer stuff we also need a module system :-/ > > FWIW we could throw it into net/lib, which has a fake target, see: > > b86761ff6374 ("selftests: net: add scaffolding for Netlink tests in Python") Oh, I see net/lib is the default dependency of everything net. This could work. I'll check it out.
diff --git a/tools/testing/selftests/net/forwarding/lib.sh b/tools/testing/selftests/net/forwarding/lib.sh index 67f38dd1f36b..21cd6a2e3344 100644 --- a/tools/testing/selftests/net/forwarding/lib.sh +++ b/tools/testing/selftests/net/forwarding/lib.sh @@ -1369,6 +1369,12 @@ tests_run() done } +cleanup() +{ + pre_cleanup + defer_scopes_cleanup +} + multipath_eval() { local desc="$1" @@ -1423,6 +1429,83 @@ in_ns() EOF } +# map[(defer_scope,cleanup_id) -> cleanup_command] +declare -A DEFERS +# map[defer_scope -> # cleanup_commands] +declare -a NDEFERS=(0) +DEFER_SCOPE=0 + +defer_scope_push() +{ + ((DEFER_SCOPE++)) + NDEFERS[${DEFER_SCOPE}]=0 +} + +defer_scope_pop() +{ + local defer_key + local defer_ix + + for ((defer_ix=${NDEFERS[${DEFER_SCOPE}]}; defer_ix-->0; )); do + defer_key=${DEFER_SCOPE},$defer_ix + ${DEFERS[$defer_key]} + unset DEFERS[$defer_key] + done + + NDEFERS[${DEFER_SCOPE}]=0 + ((DEFER_SCOPE--)) +} + +defer() +{ + local defer_key=${DEFER_SCOPE},${NDEFERS[${DEFER_SCOPE}]} + local defer="$@" + + DEFERS[$defer_key]="$defer" + NDEFERS[${DEFER_SCOPE}]=$((${NDEFERS[${DEFER_SCOPE}]} + 1)) +} + +defer_scopes_cleanup() +{ + while ((DEFER_SCOPE >= 0)); do + defer_scope_pop + done +} + +defer_scoped_fn() +{ + local name=$1; shift; + local mangle=__defer_scoped__ + + declare -f $name >/dev/null + if (($?)); then + echo "Cannot make non-existent function '$name' defer-scoped" \ + > /dev/stderr + exit 1 + fi + + declare -f $mangle$name + if ((! $?)); then + echo "The function '$name' appears to already be defer-scoped" \ + > /dev/stderr + exit 1 + fi + + eval "$mangle$(declare -f $name)" + local body=" + $name() { + local ret; + defer_scope_push; + $mangle$name \"\$@\"; + ret=\$?; + defer_scope_pop; + return \$ret; + } + " + unset $name + eval "$body" +} + ############################################################################## # Tests
In commit 8510801a9dbd ("selftests: drv-net: add ability to schedule cleanup with defer()"), a defer helper was added to Python selftests. The idea is to keep cleanup commands close to their dirtying counterparts, thereby making it more transparent what is cleaning up what, making it harder to miss a cleanup, and make the whole cleanup business exception safe. All these benefits are applicable to bash as well, exception safety can be interpreted in terms of safety vs. a SIGINT. This patch therefore introduces a framework of several helpers that serve to schedule cleanups in bash selftests: - defer_scope_push(), defer_scope_pop(): Deferred statements can be batched together in scopes. When a scope is popped, the deferred commands schoduled in that scope are executed in the order opposite to order of their scheduling. - defer(): Schedules a defer to the most recently pushed scope (or the default scope if none was pushed.) - defer_scopes_cleanup(): Pops any unpopped scopes, including the default one. The selftests that use defer should run this in their cleanup function. This is important to get cleanups of interrupted scripts. Consistent use of defers however obviates the need for a separate cleanup function -- everything is just taken care of in defers. So this patch actually introduces a cleanup() helper in the forwarding lib.sh, which calls just pre_cleanup() and defer_scopes_cleanup(). Selftests are obviously still free to override the function. - defer_scoped_fn(): Sometimes a function would like to introduce a new defer scope, then run whatever it is that it wants to run, and then pop the scope to run the deferred cleanups. The helper defer_scoped_fn() can be used to derive from one function its wrapper that pushes a defer scope before the function is called, and pops it after it returns. The following patches will convert several selftests to this new framework. Signed-off-by: Petr Machata <petrm@nvidia.com> --- tools/testing/selftests/net/forwarding/lib.sh | 83 +++++++++++++++++++ 1 file changed, 83 insertions(+)