On Fri, Nov 22, 2013 at 3:24 PM, Jeff Trawick <traw...@gmail.com> wrote:
> On Fri, Nov 22, 2013 at 2:52 PM, Jim Jagielski <j...@jagunet.com> wrote: > >> Note, the only think changed in event now (via >> https://svn.apache.org/viewvc?view=revision&revision=1542560) >> is that event *checks* that atomics work as required for >> event... if the check fails, it means that event has >> been "broken" on that system, assuming it ever hit >> blocked idlers, for a *long* time... >> > > Got it... fdqueue.c is asking for trouble... > > I'm using atomic/unix/ia32.c with icc too. > > Need to compare generated code... I hate stuff like "int foo() { unsigned > char x; ... return x; }" > > APR is documented as returning "zero if the value becomes zero on decrement, otherwise non-zero". With gcc we use get __sync_sub_and_fetch(), which returns the new value after the decrement. With icc we use the assembler implementation in APR. I think that's returning 1 instead of -1. Here is where fdqueue needs to be able to see a negative return code: apr_status_t ap_queue_info_try_get_idler(fd_queue_info_t * queue_info) { int prev_idlers; prev_idlers = apr_atomic_dec32((apr_uint32_t *)&(queue_info->idlers)); if (prev_idlers <= 0) { apr_atomic_inc32((apr_uint32_t *)&(queue_info->idlers)); /* back out dec */ return APR_EAGAIN; } return APR_SUCCESS; } ("prev" in the ia32.c version of apr_atomic_dec32() and "prev_idlers" here is deceiving.) > >> >> You should be seeing it in trunk as well... >> >> >> On Nov 22, 2013, at 2:43 PM, Jeff Trawick <traw...@gmail.com> wrote: >> >> > On Fri, Nov 22, 2013 at 2:39 PM, Jim Jagielski <j...@jagunet.com> wrote: >> > >> > On Nov 22, 2013, at 2:22 PM, Jeff Trawick <traw...@gmail.com> wrote: >> > >> > > On Sat, Nov 17, 2012 at 6:00 AM, Ruediger Pluem <rpl...@apache.org> >> wrote: >> > > >> > > >> > > j...@apache.org wrote: >> > > > + i = apr_atomic_dec32(&foo); >> > > > + if (i >= 0) { >> > > >> > > Why can we expect i < 0? apr_atomic_dec32 returns 0 if the dec causes >> foo to become zero and it returns non zero >> > > otherwise. Shouldn't this behavior the same across all platforms? And >> if not should that be fixed in APR? >> > > >> > > icc (Intel) builds of httpd 2.4.7 event MPM (with apr-1.5.0) bomb >> here. >> > > >> > > --enable-nonportable-atomics is specified for apr, though I haven't >> checked what that does with icc. >> > > >> > >> > As noted back with the orig update, this test is due to the >> > fdqueue code in the new event: >> > >> > apr_status_t ap_queue_info_set_idle(fd_queue_info_t * queue_info, >> > apr_pool_t * pool_to_recycle) >> > { >> > apr_status_t rv; >> > int prev_idlers; >> > >> > ap_push_pool(queue_info, pool_to_recycle); >> > >> > /* Atomically increment the count of idle workers */ >> > /* >> > * TODO: The atomics expect unsigned whereas we're using signed. >> > * Need to double check that they work as expected or else >> > * rework how we determine blocked. >> > * UPDATE: Correct operation is performed during open_logs() >> > */ >> > prev_idlers = apr_atomic_inc32((apr_uint32_t >> *)&(queue_info->idlers)); >> > >> > /* If other threads are waiting on a worker, wake one up */ >> > if (prev_idlers < 0) { >> > >> > >> > See the comments ("The atomics expect unsigned whereas...") for >> > the reason, etc. >> > >> > When you say "icc (Intel) builds of httpd 2.4.7 event MPM (with >> apr-1.5.0) bomb here." >> > do you mean that you get the 'atomics not working as expected' error >> > (and the internal server error) or that it core dumps? >> > >> > >> > "atomics not working as expected" >> > >> > Let me see what code is used... >> > >> > -- >> > Born in Roswell... married an alien... >> > http://emptyhammock.com/ >> >> > > > -- > Born in Roswell... married an alien... > http://emptyhammock.com/ > -- Born in Roswell... married an alien... http://emptyhammock.com/
