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From b48894ebfc1e123ec9030bb7a31a269d13995ce0 Mon Sep 17 00:00:00 2001
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From: Jonathan Lebon <jlebon@redhat.com>
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Date: Sat, 30 Nov 2013 11:14:25 -0500
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Subject: BZ1054956: stapsh.c: fix handling of POLLIN to indicate EOF
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We previously relied on POLLHUP to indicate EOF. However, it is also
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possible to receive POLLIN when EOF is reached. With this patch, upon
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receiving POLLIN and reading from the associated fd, if EOF is found, we
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modify the polling array to indicate we're no longer interested.
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---
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staprun/stapsh.c | 27 ++++++++++++++++++++-------
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1 file changed, 20 insertions(+), 7 deletions(-)
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diff --git a/staprun/stapsh.c b/staprun/stapsh.c
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index 3d88537..5c3229b 100644
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--- a/staprun/stapsh.c
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+++ b/staprun/stapsh.c
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@@ -638,7 +638,11 @@ process_command(void)
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// stap commands are short and always end in \n. Even if we do block it's not
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// so bad a thing.
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if (fgets(command, sizeof(command), stapsh_in) == NULL)
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- return;
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+ {
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+ if (feof(stapsh_in)) // no more stap commands coming
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+ pfds[PFD_STAP_OUT].events = 0;
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+ return;
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+ }
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dbug(1, "command: %s", command);
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const char* arg = strtok(command, STAPSH_TOK_DELIM) ?: "(null)";
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@@ -665,10 +669,10 @@ process_command(void)
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}
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static void
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-prefix_staprun(int fdin, FILE *out, const char *stream)
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+prefix_staprun(int i, FILE *out, const char *stream)
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{
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char buf[4096];
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- ssize_t n = read(fdin, buf, sizeof buf);
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+ ssize_t n = read(pfds[i].fd, buf, sizeof buf);
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if (n > 0)
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{
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// actually check if we need to prefix data (we could also be piping for
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@@ -679,6 +683,8 @@ prefix_staprun(int fdin, FILE *out, const char *stream)
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dbug(2, "failed fwrite\n"); // appease older gccs (don't ignore fwrite rc)
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fflush(out);
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}
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+ else if (n == 0) // eof
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+ pfds[i].events = 0;
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}
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int
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@@ -751,17 +757,24 @@ main(int argc, char* const argv[])
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sleep(2); // Once we support only platforms with guaranteed SIGIO support,
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// we could replace this with a pause().
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- for (;;)
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+ // keep polling as long as we're listening for stap commands
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+ while (pfds[PFD_STAP_OUT].events)
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{
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- poll(pfds, staprun_pid > 0 ? 3 : 1, -1);
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+ if (poll(pfds, 3, -1) < 0)
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+ {
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+ if (errno == EINTR)
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+ continue; // go back to poll()
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+ else
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+ die ("poll() failed with critical error");
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+ }
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if (pfds[PFD_STAP_OUT].revents & POLLHUP)
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break;
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if (pfds[PFD_STAP_OUT].revents & POLLIN)
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process_command();
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if (pfds[PFD_STAPRUN_OUT].revents & POLLIN)
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- prefix_staprun(pfds[PFD_STAPRUN_OUT].fd, stapsh_out, "stdout");
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+ prefix_staprun(PFD_STAPRUN_OUT, stapsh_out, "stdout");
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if (pfds[PFD_STAPRUN_ERR].revents & POLLIN)
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- prefix_staprun(pfds[PFD_STAPRUN_ERR].fd, stapsh_err, "stderr");
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+ prefix_staprun(PFD_STAPRUN_ERR, stapsh_err, "stderr");
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}
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cleanup(0);
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--
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1.8.3.1
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