port_create race test and fix #215
Open
+270
−7
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This change adds a test to the port_tests suite to trigger the port_create() race. When tested with an SMP (3) qemu instance, the race is discovered in less than twenty iterations and often much sooner.
In the current design, ports may be created with the same name because of time-of-check-time-of-use behavior. This change adds a new port magic, PORTHOLD_MAGIC, which cannot be accessed using the normal accessors. It is injected into the list upon a successful, locked search for a name. It holds the name until the allocation happens. At which point the port-hold is deleted and the real port is added while, again, under the thread lock. This change assumes using a stack-allocated port is desirable over preallocating and freeing on each port_create(). If the overhead of allocation is low, then pre-allocating the new port would be the cleanest option: (1) allocate, (2) check for collisions, (3) add to list. This fix is confirmed by the two_threads_race test completing its 256 iterations without a race. It also fixes the test to expect ERR_BUSY and to exit cleanly, as it had never completed before.
travisg
reviewed
Dec 22, 2017
app/tests/port_tests.c
Outdated
| @@ -291,6 +291,244 @@ static int ping_pong_thread(void *arg) | |||
| return __LINE__; | |||
| } | |||
|
|
|||
| const char *kStatusPortNames[] = { | |||
There was a problem hiding this comment.
make sure all of these are static so the compiler/linker will strip them if not building with the console.
There was a problem hiding this comment.
Reposting with that change now -- thanks!
There was a problem hiding this comment.
(Some of the functions in there can be made static too and I can make/test that for this pull or just do a second. Whichever works!)
This change makes the shared constants static as well as const-ifies shared packets.
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
port_create() has a known race condition in name reservation because of the separation of name uniqueness validation and name addition. This pull request adds a test that verifies the race is reachable, fixes the race, and updates the test with slight changes to support it.