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Subject: Re: [OMPI devel] [OMPI svn] svn:open-mpi r29465 - trunk/ompi/communicator
From: Ralph Castain (rhc_at_[hidden])
Date: 2013-10-22 11:46:16


I may be missing it, but it looks to me like the lock is taken right before the list manipulation. All he did was add a check for re-entry before taking the lock.

On Oct 22, 2013, at 8:39 AM, George Bosilca <bosilca_at_[hidden]> wrote:

> This patch is not correct, the list manipulation should remain protected behind the mutex.
>
> George.
>
> On Oct 22, 2013, at 17:33 , svn-commit-mailer_at_[hidden] wrote:
>
>> Author: hjelmn (Nathan Hjelm)
>> Date: 2013-10-22 11:33:39 EDT (Tue, 22 Oct 2013)
>> New Revision: 29465
>> URL: https://svn.open-mpi.org/trac/ompi/changeset/29465
>>
>> Log:
>> Fix rentry check in communicator request progress.
>>
>> cmr=v1.7.4:ticket=3796
>>
>> Text files modified:
>> trunk/ompi/communicator/comm_request.c | 9 ++++++++-
>> 1 files changed, 8 insertions(+), 1 deletions(-)
>>
>> Modified: trunk/ompi/communicator/comm_request.c
>> ==============================================================================
>> --- trunk/ompi/communicator/comm_request.c Tue Oct 22 11:33:32 2013 (r29464)
>> +++ trunk/ompi/communicator/comm_request.c 2013-10-22 11:33:39 EDT (Tue, 22 Oct 2013) (r29465)
>> @@ -11,6 +11,8 @@
>>
>> #include "comm_request.h"
>>
>> +#include "opal/include/opal/sys/atomic.h"
>> +
>> opal_free_list_t ompi_comm_requests;
>> opal_list_t ompi_comm_requests_active;
>> opal_mutex_t ompi_comm_request_mutex;
>> @@ -89,11 +91,15 @@
>> static int ompi_comm_request_progress (void)
>> {
>> ompi_comm_request_t *request, *next;
>> + static int32_t progressing = 0;
>>
>> - if (opal_mutex_trylock (&ompi_comm_request_mutex)) {
>> + /* don't allow re-entry */
>> + if (opal_atomic_swap_32 (&progressing, 1)) {
>> return 0;
>> }
>>
>> + opal_mutex_lock (&ompi_comm_request_mutex);
>> +
>> OPAL_LIST_FOREACH_SAFE(request, next, &ompi_comm_requests_active, ompi_comm_request_t) {
>> int rc = OMPI_SUCCESS;
>>
>> @@ -140,6 +146,7 @@
>> }
>>
>> opal_mutex_unlock (&ompi_comm_request_mutex);
>> + progressing = 0;
>>
>> return 1;
>> }
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