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ULE: provide defaults to ts_cpu

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Fix a bug when the system has no CPU 0. When created, threads were implicitly assigned to CPU 0.
This had no practical effect since a real CPU was chosen immediately by the scheduler. However,
on systems without a CPU 0, sched_ule attempted to access the scheduler queue of the "old" CPU
when assigned the initial choice of the old one. This caused an attempt to use illegal memory
and a crash (or, more usually, a deadlock). Fix this by assigned new threads to the BSP
explicitly and add some asserts to see that this problem does not recur.

Authored by:           Nathan Whitehorn <nwhitehorn@freebsd.org>
Submitted by:          Wojciech Macek <wma@semihalf.com>
Obtained from:         Semihalf
Differential revision: https://reviews.freebsd.org/D13932
This commit is contained in:
Wojciech Macek 2018-01-24 07:54:05 +00:00
parent 53362abb8e
commit 4d249cdd4c
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=328320
1 changed files with 2 additions and 0 deletions
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2
sys/kern/sched_ule.c
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@ -1405,6 +1405,7 @@ sched_setup(void *dummy)
/* Add thread0's load since it's running. */
TDQ_LOCK(tdq);
td_get_sched(&thread0)->ts_cpu = curcpu; /* Something valid to start */
thread0.td_lock = TDQ_LOCKPTR(TDQ_SELF());
tdq_load_add(tdq, &thread0);
tdq->tdq_lowpri = thread0.td_priority;
@ -2454,6 +2455,7 @@ sched_add(struct thread *td, int flags)
* Pick the destination cpu and if it isn't ours transfer to the
* target cpu.
*/
td_get_sched(td)->ts_cpu = curcpu; /* Pick something valid to start */
cpu = sched_pickcpu(td, flags);
tdq = sched_setcpu(td, cpu, flags);
tdq_add(tdq, td, flags);