diff options
Diffstat (limited to 'open_issues/libpthread_pthread_key_create_reuse.mdwn')
| -rw-r--r-- | open_issues/libpthread_pthread_key_create_reuse.mdwn | 66 |
1 files changed, 1 insertions, 65 deletions
diff --git a/open_issues/libpthread_pthread_key_create_reuse.mdwn b/open_issues/libpthread_pthread_key_create_reuse.mdwn index ca2da2f5..ea6a0abf 100644 --- a/open_issues/libpthread_pthread_key_create_reuse.mdwn +++ b/open_issues/libpthread_pthread_key_create_reuse.mdwn @@ -8,75 +8,11 @@ Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled [[GNU Free Documentation License|/fdl]]."]]"""]] -[[!meta title="libpthread: pthread_key_create, reuse"]] +[[!meta title="libpthread vs. licq"]] [[!tag open_issue_libpthread]] IRC, FreeNode, #hurd, 2011-07-02: - < pinotree> hm, maybe i found a libpthread bug - * pinotree tries a testcase - < pinotree> yesssss, found the bug :) - < pinotree> youpi: it's a problem of the key reuse in pthread_key_create() - < youpi> it doesn't reset it? - < youpi> were you looking at the licq issue? - < pinotree> no, gtest - < youpi> k < youpi> licq has a failing threadspecific issue < youpi> [ FAILED ] ThreadSpecificData.dataDeletedWhenThreadExits - < pinotree> basically, pthread_key_delete() does not delete the key values - from the "thread_specifics" ihash - < pinotree> but those were new keys, so i'm not sure it is allowed to - return values of previous keys? - < pinotree> after all, the actual key value is an implementation detail, - applications shouldn't care about it being reused - < pinotree> (imho) - < youpi> Upon key creation, the value NULL shall be associated with the new - key in all active threads. - < youpi> ok, so we have to clear it in all threads - < youpi> that's a pity - < pinotree> or just remove the entry from the hash on key removal - < youpi> pinotree: from all the hashes, you mean? - < pinotree> youpi: from how i see it, adding a snippet like - http://paste.debian.net/121690/ in pthread_key_delete() should do the job - < youpi> that only drops from the current thread - < pinotree> ah hm, other threads - < youpi> we need to drop from all threads - < youpi> that's the pity part - < pinotree> youpi: the licq case could look like a similar issue, at a - veeery quick glance - -Test program: [[pthread_key_create_reuse.c]] - - -2011-11-01: - - <pinotree> youpi: about the bug with pthread keys (reuse): would be an - acceptable solution having a mutex for the thread_specifics of each - thread? - <youpi> you mean one per thread, one global, or one per key, or ? - <youpi> what is it supposed to protect? - <pinotree> the thread_specifics of each thread - <youpi> pinotree: but against what? - <pinotree> the idea would be: when destroying a key, iterate over all the - exiting threads and remove the key data from the thread_specifics of each - thread - <youpi> one of the issue is getting to browse through the whole list of - threads - <youpi> the other is concurrency between that, and a thread dying - <pinotree> there's the __pthread_threads_lock rwlock - <youpi> it should be enough to keep it locked during the iteration - <pinotree> but that wouldn't be enough when one thread is destroying a key, - and another one is doing {get,set}specific() on that key - <youpi> that's not supposed to happen - <pinotree> mmm - <youpi> “The effect of calling pthread_getspecific() or - pthread_setspecific() with a key value not obtained from - pthread_key_create() or after key has been deleted with - pthread_key_delete() is undefined.” - <youpi> undefined -> you are allowed to just blow up - <pinotree> but it's not been deleted yet... :) - <youpi> it could be, just a matter of time - <youpi> you're not supposed to rely on time-luckyness :) - <pinotree> mmm - <pinotree> bah, you've convinced me ( :) ) |