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| author | Renato Botelho <renato@netgate.com> | 2017-02-09 11:26:48 -0200 |
|---|---|---|
| committer | Renato Botelho <renato@netgate.com> | 2017-02-09 11:26:48 -0200 |
| commit | 4a05f5440acda223e6a0ec5157bc32ecc0f09ff9 (patch) | |
| tree | 4c2ece480e5d4155ed35bec62996de40eb179f18 /sys/kern/kern_switch.c | |
| parent | 681a482d8fc4bfc14a24f7a9d75cca6337f2a520 (diff) | |
| parent | a1e52233c91fd46e666297270ab655f1abff8535 (diff) | |
| download | FreeBSD-src-4a05f5440acda223e6a0ec5157bc32ecc0f09ff9.zip FreeBSD-src-4a05f5440acda223e6a0ec5157bc32ecc0f09ff9.tar.gz | |
Merge remote-tracking branch 'origin/stable/10' into devel
Diffstat (limited to 'sys/kern/kern_switch.c')
| -rw-r--r-- | sys/kern/kern_switch.c | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/sys/kern/kern_switch.c b/sys/kern/kern_switch.c index d0009b1..f58acd5 100644 --- a/sys/kern/kern_switch.c +++ b/sys/kern/kern_switch.c @@ -206,7 +206,22 @@ critical_exit(void) if (td->td_critnest == 1) { td->td_critnest = 0; + + /* + * Interrupt handlers execute critical_exit() on + * leave, and td_owepreempt may be left set by an + * interrupt handler only when td_critnest > 0. If we + * are decrementing td_critnest from 1 to 0, read + * td_owepreempt after decrementing, to not miss the + * preempt. Disallow compiler to reorder operations. + */ + __compiler_membar(); if (td->td_owepreempt && !kdb_active) { + /* + * Microoptimization: we committed to switch, + * disable preemption in interrupt handlers + * while spinning for the thread lock. + */ td->td_critnest = 1; thread_lock(td); td->td_critnest--; |
