[Xen-changelog] [xen stable-4.2] tools/blktap2: Handle read/write interrupts in blktap2 control plane.

[patchbot@xxxxxxx]

commit a2065070a0fe4fdf6580b2f31ba069184136e924
Author:     Dr. Greg Wettstein <greg@xxxxxxxxxxxxxxxxx>
AuthorDate: Thu Mar 28 07:50:34 2013 +0000
Commit:     Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
CommitDate: Mon Apr 15 18:08:37 2013 +0100

    tools/blktap2: Handle read/write interrupts in blktap2 control plane.
    
    The following patch:
    
    tools: Retry blktap2 tapdisk message on interrupt.
    
    Addressed a long standing regression with the blktap2 control
    plane.  An interruption of the select system call would
    prematurely terminate the message sequence needed to properly
    shutdown a blktap2 tapdisk instance.
    
    Ian Jackson correctly noted that the read and write systems calls
    responsible for receiving and sending the control messages could
    also return EINTR resulting in similar effects.  While this
    regression was not noted in field testing this patch adds support
    to re-start the calls to provide a technically complete
    implementation of control plane management in the presence of
    signals.
    
    Signed-off-by: Dr. Greg Wettstein <xen@xxxxxxxxxxxxxxxxx>
    Acked-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
    (cherry picked from commit a5c800142cfc82159fcb85b47116cf296caebcc5)
---
 tools/blktap2/control/tap-ctl-ipc.c |   10 ++++++++--
 1 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/tools/blktap2/control/tap-ctl-ipc.c 
b/tools/blktap2/control/tap-ctl-ipc.c
index c8aad1c..c7e42d9 100644
--- a/tools/blktap2/control/tap-ctl-ipc.c
+++ b/tools/blktap2/control/tap-ctl-ipc.c
@@ -71,8 +71,11 @@ tap_ctl_read_message(int fd, tapdisk_message_t *message, int 
timeout)
                }
                else if (FD_ISSET(fd, &readfds)) {
                        ret = read(fd, message + offset, len - offset);
-                       if (ret <= 0)
+                       if (ret <= 0) {
+                               if (errno == EINTR)
+                                       continue;
                                break;
+                       }
                        offset += ret;
                } else
                        break;
@@ -124,8 +127,11 @@ tap_ctl_write_message(int fd, tapdisk_message_t *message, 
int timeout)
                }
                else if (FD_ISSET(fd, &writefds)) {
                        ret = write(fd, message + offset, len - offset);
-                       if (ret <= 0)
+                       if (ret <= 0) {
+                               if (errno == EINTR)
+                                       continue;
                                break;
+                       }
                        offset += ret;
                } else
                        break;
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.2

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