Messages in this thread | | | Date | Wed, 22 Jul 2020 09:41:34 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH v12 05/15] perf evlist: implement control command handling functions |
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Em Fri, Jul 17, 2020 at 10:01:33AM +0300, Alexey Budankov escreveu: > > Implement functions of initialization, finalization and processing > of control command messages coming from control file descriptors. > Allocate control file descriptor as descriptor at struct pollfd > object of evsel_list for atomic poll() operation. > > Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com> > Acked-by: Jiri Olsa <jolsa@redhat.com> > Acked-by: Namhyung Kim <namhyung@kernel.org> > --- > tools/perf/util/evlist.c | 140 +++++++++++++++++++++++++++++++++++++++ > tools/perf/util/evlist.h | 18 +++++ > 2 files changed, 158 insertions(+) > > diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c > index 36eb50aba1f5..fe900d82815c 100644 > --- a/tools/perf/util/evlist.c > +++ b/tools/perf/util/evlist.c > @@ -1714,3 +1714,143 @@ struct evsel *perf_evlist__reset_weak_group(struct evlist *evsel_list, > } > return leader; > } > + > +int evlist__initialize_ctlfd(struct evlist *evlist, int fd, int ack) > +{ > + if (fd == -1) { > + pr_debug("Control descriptor is not initialized\n"); > + return 0; > + } > + > + evlist->ctl_fd.pos = perf_evlist__add_pollfd(&evlist->core, fd, NULL, POLLIN, > + fdarray_flag__nonfilterable); > + if (evlist->ctl_fd.pos < 0) { > + evlist->ctl_fd.pos = -1; > + pr_err("Failed to add ctl fd entry: %m\n"); > + return -1; > + } > + > + evlist->ctl_fd.fd = fd; > + evlist->ctl_fd.ack = ack; > + > + return 0; > +} > + > +bool evlist__ctlfd_initialized(struct evlist *evlist) > +{ > + return evlist->ctl_fd.pos >= 0; > +} > + > +int evlist__finalize_ctlfd(struct evlist *evlist) > +{ > + struct pollfd *entries = evlist->core.pollfd.entries; > + > + if (!evlist__ctlfd_initialized(evlist)) > + return 0; > + > + entries[evlist->ctl_fd.pos].fd = -1; > + entries[evlist->ctl_fd.pos].events = 0; > + entries[evlist->ctl_fd.pos].revents = 0; > + > + evlist->ctl_fd.pos = -1; > + evlist->ctl_fd.ack = -1; > + evlist->ctl_fd.fd = -1; > + > + return 0; > +} > + > +static int evlist__ctlfd_recv(struct evlist *evlist, enum evlist_ctl_cmd *cmd, > + char *cmd_data, size_t data_size) > +{ > + int err; > + char c; > + size_t bytes_read = 0; > + > + memset(cmd_data, 0, data_size); > + data_size--; > + > + do { > + err = read(evlist->ctl_fd.fd, &c, 1); > + if (err > 0) { > + if (c == '\n' || c == '\0') > + break; > + cmd_data[bytes_read++] = c; > + if (bytes_read == data_size) > + break; > + } else { > + if (err == -1) > + pr_err("Failed to read from ctlfd %d: %m\n", evlist->ctl_fd.fd); > + break; > + } > + } while (1);
Ok, here you don't know how many bytes you have to read, the protocol is a string ending in \n or \0, so you can't use 'readn()', but see below for the write() case.
Also is this ctf_fd in non-blocking mode? Can't this get stuck waiting forever?
> + pr_debug("Message from ctl_fd: \"%s%s\"\n", cmd_data, > + bytes_read == data_size ? "" : c == '\n' ? "\\n" : "\\0"); > + > + if (err > 0) { > + if (!strncmp(cmd_data, EVLIST_CTL_CMD_ENABLE_TAG, > + (sizeof(EVLIST_CTL_CMD_ENABLE_TAG)-1))) { > + *cmd = EVLIST_CTL_CMD_ENABLE; > + } else if (!strncmp(cmd_data, EVLIST_CTL_CMD_DISABLE_TAG, > + (sizeof(EVLIST_CTL_CMD_DISABLE_TAG)-1))) { > + *cmd = EVLIST_CTL_CMD_DISABLE; > + } > + } > + > + return err; > +} > + > +static int evlist__ctlfd_ack(struct evlist *evlist) > +{ > + int err; > + > + if (evlist->ctl_fd.ack == -1) > + return 0; > + > + err = write(evlist->ctl_fd.ack, EVLIST_CTL_CMD_ACK_TAG, > + sizeof(EVLIST_CTL_CMD_ACK_TAG)); > + if (err == -1) > + pr_err("failed to write to ctl_ack_fd %d: %m\n", evlist->ctl_fd.ack);
Also the function to use here is 'writen()':
/* * Write exactly 'n' bytes or return an error. */ ssize_t writen(int fd, const void *buf, size_t n) { /* ion does not modify buf. */ return ion(false, fd, (void *)buf, n); } "tools/lib/perf/lib.c"
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I.e. libperf's fd based fwrite().
Again, this can be done on top of this patch set, so I'll continue as-is.
- Arnaldo
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