On 10/22/2013 11:16 PM, Jason Evans wrote:
On Oct 21, 2013, at 2:12 PM, Leonard Crestez <[email protected]> wrote:
When using LinuxThreads pthread_setspecific triggers recursive allocation on
all threads. Work around this by creating a global linked list of in-progress
tsd initializations.
This modifies the _tsd_get_wrapper macro-generated function. When it has
to initialize an TSD object it will push the item to the linked list
first. If this causes a recursive allocation then the _get_wrapper
request is satisfied from the list. When pthread_setspecific returns the item
is removed from the list.
This effectively adds a very poor substitute for real TLS used only
during pthread_setspecific allocation recursion.
Signed-off-by: Crestez Dan Leonard <[email protected]>
---
include/jemalloc/internal/tsd.h | 63 +++++++++++++++++++++++++++++++++++++++++
1 file changed, 63 insertions(+)
I don't see how this code can work. It stack-allocates block (struct
tsd_init_block block;), then permanently links it into a ring. There are other
less critical issues (e.g. no cleanup during thread exit, using pthread_mutex_t
rather than malloc_mutex_t, and coding style conformance), but let's worry
first about whether there's a feasible way to restructure the initialization
code.
Hello,
The link is not permanent, it is temporary until pthread_setspecific
returns. The stack-allocated block is inserted in the list by
tsd_init_checkrec and removed by tsd_init_finish, immediately after
pthread_setspecific returns. It is allocated on the stack because the
lifetime is so short. Unless a lot of threads are created the list will
only contain at most one item during the first allocation on each thread.
I can replace pthread_mutex_t. What should I fix about the coding style
to make it acceptable? Should I move the tsd_init_* inside the
malloc_tsd_funcs macro or to some separate file?
Regards,
Leonard
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