| Message ID | 20191205223008.8623-7-andrew.cooper3@citrix.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | xen: Support continuations from tasklets | expand |
On 05.12.2019 23:30, Andrew Cooper wrote: > --- a/xen/arch/x86/sysctl.c > +++ b/xen/arch/x86/sysctl.c > @@ -85,6 +85,9 @@ long cpu_up_helper(void *data) > /* On EBUSY, flush RCU work and have one more go. */ > rcu_barrier(); > ret = cpu_up(cpu); > + > + if ( ret == -EBUSY ) > + ret = -ERESTART; > } > > if ( !ret && !opt_smt && > @@ -110,6 +113,9 @@ long cpu_down_helper(void *data) > /* On EBUSY, flush RCU work and have one more go. */ > rcu_barrier(); > ret = cpu_down(cpu); > + > + if ( ret == -EBUSY ) > + ret = -ERESTART; > } > return ret; > } For both of these - if two successive attempts didn't work, is there really much point not reporting the fact back to the caller? You're liable to request continuations indefinitely then. > @@ -143,8 +149,7 @@ static long smt_up_down_helper(void *data) > */ > if ( ret != -EEXIST && general_preempt_check() ) > { > - /* In tasklet context - can't create a contination. */ > - ret = -EBUSY; > + ret = -ERESTART; > break; > } > I agree with this change. Jan
diff --git a/xen/arch/x86/sysctl.c b/xen/arch/x86/sysctl.c index 4a76f0f47f..06955fdc3e 100644 --- a/xen/arch/x86/sysctl.c +++ b/xen/arch/x86/sysctl.c @@ -85,6 +85,9 @@ long cpu_up_helper(void *data) /* On EBUSY, flush RCU work and have one more go. */ rcu_barrier(); ret = cpu_up(cpu); + + if ( ret == -EBUSY ) + ret = -ERESTART; } if ( !ret && !opt_smt && @@ -110,6 +113,9 @@ long cpu_down_helper(void *data) /* On EBUSY, flush RCU work and have one more go. */ rcu_barrier(); ret = cpu_down(cpu); + + if ( ret == -EBUSY ) + ret = -ERESTART; } return ret; } @@ -143,8 +149,7 @@ static long smt_up_down_helper(void *data) */ if ( ret != -EEXIST && general_preempt_check() ) { - /* In tasklet context - can't create a contination. */ - ret = -EBUSY; + ret = -ERESTART; break; }
Tasklet context is now capable of using handling continuations. Use this rather than -EBUSY as it is a more efficient way to restart the hypercall. Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com> --- CC: Jan Beulich <JBeulich@suse.com> CC: Wei Liu <wl@xen.org> CC: Roger Pau Monné <roger.pau@citrix.com> --- xen/arch/x86/sysctl.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)