Do a lockless check in kthread_suspend_check
Otherwise an idle system running lockstat sleep 10 reports contention on process lock comming from bufdaemon. While here fix a style nit.
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svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=363511
@ -441,12 +441,15 @@ kthread_suspend_check(void)
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panic("%s: curthread is not a valid kthread", __func__);
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/*
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* As long as the double-lock protection is used when accessing the
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* TDF_KTH_SUSP flag, synchronizing the read operation via proc mutex
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* is fine.
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* Setting the TDF_KTH_SUSP flag is protected by process lock.
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*
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* Do an unlocked read first to avoid serializing with all other threads
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* in the common case of not suspending.
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*/
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if ((td->td_flags & TDF_KTH_SUSP) == 0)
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return;
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PROC_LOCK(p);
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while (td->td_flags & TDF_KTH_SUSP) {
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while ((td->td_flags & TDF_KTH_SUSP) != 0) {
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wakeup(&td->td_flags);
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msleep(&td->td_flags, &p->p_mtx, PPAUSE, "ktsusp", 0);
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}
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