SPE to SPE signaling

From Cellbe

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This tutorial shows  how to send signals from one spe to another.
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Denny,There IS a bug in the incrementing of the major vsoeirn.  I've fixed it in SVN, but haven't made a new public release with the fix (one more entry on my list of things to do "sometime").  Since the major vsoeirn only updates between migrations, the bug can only manifest itself if there is an issue with the first step of a given migration, but you're right, there is an issue there.  The minor vsoeirns (steps within a migration) are double protected: the increment happens second, and the whole thing is wrapped in a CFTRANSACTION.  The reason the major vsoeirn increments first is for internal bookkeeping reasons.  It's safe for it to increment even if the first migration step fails, because it'll be minor vsoeirn zero (which means the first step is still next in line).  The bug was in when the minor vsoeirn was reset to zero; it happened at the wrong time before.For the two-developer conflict scenario, there's nothing the tool can do about it. You have to resolve the conflicts when the second developer commits his/her changes. Migration code does have some ordering ramifications, so resolving a conflict might not be as simple as otherwise (quite possibly requiring manual tweaks to the `schema_version` table), but it's really no different from any other conflict between multiple developers.
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There are three entities in this tutorial:
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*'''starter''': the PPE process who starts the spe threads
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*'''sender''': the SPE thread who sends the signal
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*'''receiver''' the SPE thread who receives the signal
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WAN Clustering allows you to scpfiey alternate IP's for NetConnect profiles, since they may differ on a cluster member at a remote site.  If WAN Cluster is being deprecated then there needs to be a way to map a role to a correct netconnect profiles for a device.  Currently there is no way to find out a unique identifier for the device (Serial Number/MAC/Device Name) to facilitate the mapping to a correct NetConnect profile.  Push Config can overwrite the incorrect NetConnect profile.  Juniper Support have been a dead end when trying to deal with this (or any enhancement).
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==PPE side: starter==
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The process '''starter''' does basically this:
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#creates the spe threads
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#sends '''sender''' the address of the signal notify area of '''receiver'''
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#joins the threads.
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It's important to note that the contexts are created using the <tt>'''SPE_MAP_PS'''</tt> flag, because we want the problem state area of the SPEs to be mapped in the effective address space (the signals are sent with dma commands).
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<pre>
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/*
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  * =============================================================================
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*      Filename:  ppusig.c
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*    Description:  starter
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*        Author:  Alessandro Piras (laynor@gmail.com)
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* =============================================================================
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*/
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#define ZZ_CTX_CREATE -2
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#define ZZ_PRG_LOAD -3
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#define ZZ_CTX_RUN -4
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#define ZZ_PTH_CREATE -5
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#define ZZ_PTH_JOIN -6
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#include <stdio.h>
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#include <libspe2.h>
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#include <pthread.h>
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#include <unistd.h>
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#include <stdlib.h>
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//#include <commonlib.h>
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extern spe_program_handle_t spurecv;
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extern spe_program_handle_t spusend;
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void *pth_rtn(void *arg)
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{
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unsigned int entry=SPE_DEFAULT_ENTRY;
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int rc;
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void *argp=NULL;
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void *envp=NULL;
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spe_context_ptr_t ctx;
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ctx = *((spe_context_ptr_t *) arg);
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rc = spe_context_run(ctx, &entry, 0, argp, envp, NULL);
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if(rc < 0) {
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perror("spe_context_run()");
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exit(ZZ_CTX_RUN);
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}
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pthread_exit(NULL);
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}
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int main()
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{
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spe_context_ptr_t ctx[2];
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pthread_t pth[2];
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unsigned int flags = SPE_MAP_PS;
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int i;
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spe_sig_notify_1_area_t *sig_area;
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unsigned int sig_area1;
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//-----CTX creation
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for(i=0; i<2; i++){
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ctx[i] = spe_context_create(flags, 0);
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if(ctx[i] == NULL){
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perror("spe_context_create()");
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exit(ZZ_CTX_CREATE);
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}
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}
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//-----PRG load
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if(spe_program_load(ctx[0],&spurecv)){
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perror("spe_program_load()");
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exit(ZZ_PRG_LOAD);
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}
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if(spe_program_load(ctx[1],&spusend)){
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perror("spe_program_load()");
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exit(ZZ_PRG_LOAD);
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}
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//-----PTH creation
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for(i=0; i<2; i++)
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if(pthread_create(&pth[i], NULL, pth_rtn, &ctx[i])){
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perror("pthread_create()");
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exit(ZZ_PTH_CREATE);
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}
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sig_area = spe_ps_area_get(ctx[0], SPE_SIG_NOTIFY_1_AREA);
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sig_area1 = (unsigned int) (&(sig_area->SPU_Sig_Notify_1));
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spe_in_mbox_write(ctx[1], &sig_area1, 1, 1);
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//-----PTH join
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for(i=0; i<2; i++)
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if(pthread_join(pth[i], NULL)){
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perror("pthread_join()");
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exit(ZZ_PTH_JOIN);
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}
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//-----CTX destruction
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for(i=0; i<2; i++)
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spe_context_destroy(ctx[i]);
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return 0;
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}
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</pre>
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It makes me sad that my immediate rietcaon is to think of the flaws in the author's arguments, because this is the sort of article we need more of. To the best of my knowledge, the pro-life stance isn't about creating a home for a stranger. That's what parenthood is about, but I don't see a direct connection to abortion. People like Marc Ouellet are pro-life because it lets them cultivate a sense of moral superiority over other people. Likewise, the entire fearmongering trend is about cultivating a sense of ethnic superiority over others. The two go together quite well.
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==SPE side: receiver==
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Not much to say here, it's pretty simple.
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<pre>
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/*
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* =============================================================================
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*      Filename:  spurecv.c
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*    Description:  Waits for a signal and prints it
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*        Author:  Alessandro Piras (laynor@gmail.com)
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* =============================================================================
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*/
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#include <spu_intrinsics.h>
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#include <spu_mfcio.h>
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#include <stdio.h>
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int main(unsigned long long spe_id __attribute__ ((unused)),
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unsigned long long argp __attribute__ ((unused)),
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unsigned long long envp __attribute__ ((unused)))
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{
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unsigned int value;
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value = spu_read_signal1();
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printf("(recvr) value: %u\
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", value);
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return 0;
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}
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</pre>
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[[Category:Tutorial]]
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Current revision as of 19:44, 20 November 2015

Denny,There IS a bug in the incrementing of the major vsoeirn. I've fixed it in SVN, but haven't made a new public release with the fix (one more entry on my list of things to do "sometime"). Since the major vsoeirn only updates between migrations, the bug can only manifest itself if there is an issue with the first step of a given migration, but you're right, there is an issue there. The minor vsoeirns (steps within a migration) are double protected: the increment happens second, and the whole thing is wrapped in a CFTRANSACTION. The reason the major vsoeirn increments first is for internal bookkeeping reasons. It's safe for it to increment even if the first migration step fails, because it'll be minor vsoeirn zero (which means the first step is still next in line). The bug was in when the minor vsoeirn was reset to zero; it happened at the wrong time before.For the two-developer conflict scenario, there's nothing the tool can do about it. You have to resolve the conflicts when the second developer commits his/her changes. Migration code does have some ordering ramifications, so resolving a conflict might not be as simple as otherwise (quite possibly requiring manual tweaks to the `schema_version` table), but it's really no different from any other conflict between multiple developers.

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