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-rw-r--r--open_issues/libpthread_pthread_key_create_reuse.mdwn66
-rw-r--r--open_issues/libpthread_pthread_key_create_reuse/pthread_key_create_reuse.c48
2 files changed, 1 insertions, 113 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 ( :) )
diff --git a/open_issues/libpthread_pthread_key_create_reuse/pthread_key_create_reuse.c b/open_issues/libpthread_pthread_key_create_reuse/pthread_key_create_reuse.c
deleted file mode 100644
index f7f5874e..00000000
--- a/open_issues/libpthread_pthread_key_create_reuse/pthread_key_create_reuse.c
+++ /dev/null
@@ -1,48 +0,0 @@
-#include <pthread.h>
-#include <stdio.h>
-#include <assert.h>
-
-#define DEBUG
-
-void del(void *x __attribute__((unused)))
-{
-}
-
-void work(int val)
-{
- pthread_key_t key1;
- pthread_key_t key2;
-
-#ifdef DEBUG
- printf("work/%d: start\n", val);
-#endif
- assert(pthread_key_create(&key1, &del) == 0);
- assert(pthread_key_create(&key2, &del) == 0);
-#ifdef DEBUG
- printf("work/%d: pre-setspecific: %p,%p\n", val, pthread_getspecific(key1), pthread_getspecific(key2));
-#else
- assert(pthread_getspecific(key1) == NULL);
- assert(pthread_getspecific(key2) == NULL);
-#endif
- assert(pthread_setspecific(key1, (void *)(0x100 + val)) == 0);
- assert(pthread_setspecific(key2, (void *)(0x200 + val)) == 0);
-#ifdef DEBUG
- printf("work/%d: post-setspecific: %p,%p\n", val, pthread_getspecific(key1), pthread_getspecific(key2));
-#else
- assert(pthread_getspecific(key1) == (void *)(0x100 + val));
- assert(pthread_getspecific(key2) == (void *)(0x200 + val));
-#endif
- assert(pthread_key_delete(key1) == 0);
- assert(pthread_key_delete(key2) == 0);
-}
-
-int main()
-{
- int i;
-
- for (i = 0; i < 8; ++i) {
- work(i + 1);
- }
-
- return 0;
-}