path: root/include/linux/stop_machine.h
diff options
authorSuresh Siddha <suresh.b.siddha@intel.com>2011-06-23 11:19:26 -0700
committerH. Peter Anvin <hpa@linux.intel.com>2011-06-27 14:00:46 -0700
commit6d3321e8e2b3bf6a5892e2ef673c7bf536e3f904 (patch)
tree4c911f90934bd755ac12f11cc2dc9070e1aead80 /include/linux/stop_machine.h
parent4699d4423c07a1db35ea9453eac3a07e818338f9 (diff)
x86, mtrr: lock stop machine during MTRR rendezvous sequence
MTRR rendezvous sequence using stop_one_cpu_nowait() can potentially happen in parallel with another system wide rendezvous using stop_machine(). This can lead to deadlock (The order in which works are queued can be different on different cpu's. Some cpu's will be running the first rendezvous handler and others will be running the second rendezvous handler. Each set waiting for the other set to join for the system wide rendezvous, leading to a deadlock). MTRR rendezvous sequence is not implemented using stop_machine() as this gets called both from the process context aswell as the cpu online paths (where the cpu has not come online and the interrupts are disabled etc). stop_machine() works with only online cpus. For now, take the stop_machine mutex in the MTRR rendezvous sequence that gets called from an online cpu (here we are in the process context and can potentially sleep while taking the mutex). And the MTRR rendezvous that gets triggered during cpu online doesn't need to take this stop_machine lock (as the stop_machine() already ensures that there is no cpu hotplug going on in parallel by doing get_online_cpus()) TBD: Pursue a cleaner solution of extending the stop_machine() infrastructure to handle the case where the calling cpu is still not online and use this for MTRR rendezvous sequence. fixes: https://bugzilla.novell.com/show_bug.cgi?id=672008 Reported-by: Vadim Kotelnikov <vadimuzzz@inbox.ru> Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> Link: http://lkml.kernel.org/r/20110623182056.807230326@sbsiddha-MOBL3.sc.intel.com Cc: stable@kernel.org # 2.6.35+, backport a week or two after this gets more testing in mainline Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Diffstat (limited to 'include/linux/stop_machine.h')
1 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/stop_machine.h b/include/linux/stop_machine.h
index 092dc9b1ce7d..14d3524d1274 100644
--- a/include/linux/stop_machine.h
+++ b/include/linux/stop_machine.h
@@ -27,6 +27,8 @@ struct cpu_stop_work {
struct cpu_stop_done *done;
+extern struct mutex stop_cpus_mutex;
int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg);
void stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
struct cpu_stop_work *work_buf);