[Xen-devel] [PATCH 1/3] libxc: Revert "do some retries in xc_cpupool_removecpu() for EBUSY case"

[Ian Jackson <ian.jackson@xxxxxxxxxxxxx>]

libxc may be called from within long-running daemons such as libvirt.

In such a system this sleep would enable an uncooperative or buggy
guest to block all toolstack operations for an extended period.

Sadly, therefore, such a retry loop is not feasible without a lot of
engineering which is probably not appropriate.

This reverts commit 1ef6beea187bca8d11152b6c7d987b2b9450f936
"libxc: do some retries in xc_cpupool_removecpu() for EBUSY case"

Signed-off-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
CC: Dario Faggioli <dario.faggioli@xxxxxxxxxx>
CC: Wei Liu <wei.liu2@xxxxxxxxxx>
---
 tools/libxc/xc_cpupool.c |   20 +-------------------
 1 file changed, 1 insertion(+), 19 deletions(-)

diff --git a/tools/libxc/xc_cpupool.c b/tools/libxc/xc_cpupool.c
index 261b9c9..c42273e 100644
--- a/tools/libxc/xc_cpupool.c
+++ b/tools/libxc/xc_cpupool.c
@@ -20,7 +20,6 @@
  */
 
 #include <stdarg.h>
-#include <unistd.h>
 #include "xc_private.h"
 
 static int do_sysctl_save(xc_interface *xch, struct xen_sysctl *sysctl)
@@ -138,34 +137,17 @@ int xc_cpupool_addcpu(xc_interface *xch,
     return do_sysctl_save(xch, &sysctl);
 }
 
-/*
- * The hypervisor might return EBUSY when trying to remove a cpu from a
- * cpupool when a domain running in this cpupool has pinned a vcpu
- * temporarily. Do some retries in this case, perhaps the situation
- * cleans up.
- */
-#define NUM_RMCPU_BUSY_RETRIES 5
-
 int xc_cpupool_removecpu(xc_interface *xch,
                          uint32_t poolid,
                          int cpu)
 {
-    unsigned retries;
-    int err;
     DECLARE_SYSCTL;
 
     sysctl.cmd = XEN_SYSCTL_cpupool_op;
     sysctl.u.cpupool_op.op = XEN_SYSCTL_CPUPOOL_OP_RMCPU;
     sysctl.u.cpupool_op.cpupool_id = poolid;
     sysctl.u.cpupool_op.cpu = (cpu < 0) ? XEN_SYSCTL_CPUPOOL_PAR_ANY : cpu;
-    for ( retries = 0; retries < NUM_RMCPU_BUSY_RETRIES; retries++ ) {
-        err = do_sysctl_save(xch, &sysctl);
-        if ( err < 0 && errno == EBUSY )
-            sleep(1);
-        else
-            break;
-    }
-    return err;
+    return do_sysctl_save(xch, &sysctl);
 }
 
 int xc_cpupool_movedomain(xc_interface *xch,
-- 
1.7.10.4


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