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author | Ingo Molnar <mingo@kernel.org> | 2018-11-03 23:42:16 +0100 |
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committer | Ingo Molnar <mingo@kernel.org> | 2018-11-03 23:42:16 +0100 |
commit | 23a12ddee1ce28065b71f14ccc695b5a0c8a64ff (patch) | |
tree | cedaa1cde5b2557116e523c31552187804704093 /arch/x86/xen/spinlock.c | |
parent | compat: Cleanup in_compat_syscall() callers (diff) | |
parent | objtool: Support GCC 9 cold subfunction naming scheme (diff) | |
download | linux-dev-23a12ddee1ce28065b71f14ccc695b5a0c8a64ff.tar.xz linux-dev-23a12ddee1ce28065b71f14ccc695b5a0c8a64ff.zip |
Merge branch 'core/urgent' into x86/urgent, to pick up objtool fix
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/xen/spinlock.c')
-rw-r--r-- | arch/x86/xen/spinlock.c | 33 |
1 files changed, 12 insertions, 21 deletions
diff --git a/arch/x86/xen/spinlock.c b/arch/x86/xen/spinlock.c index 23f6793af88a..441c88262169 100644 --- a/arch/x86/xen/spinlock.c +++ b/arch/x86/xen/spinlock.c @@ -39,34 +39,25 @@ static void xen_qlock_kick(int cpu) */ static void xen_qlock_wait(u8 *byte, u8 val) { + unsigned long flags; int irq = __this_cpu_read(lock_kicker_irq); /* If kicker interrupts not initialized yet, just spin */ - if (irq == -1) + if (irq == -1 || in_nmi()) return; - /* clear pending */ - xen_clear_irq_pending(irq); - barrier(); - - /* - * We check the byte value after clearing pending IRQ to make sure - * that we won't miss a wakeup event because of the clearing. - * - * The sync_clear_bit() call in xen_clear_irq_pending() is atomic. - * So it is effectively a memory barrier for x86. - */ - if (READ_ONCE(*byte) != val) - return; + /* Guard against reentry. */ + local_irq_save(flags); - /* - * If an interrupt happens here, it will leave the wakeup irq - * pending, which will cause xen_poll_irq() to return - * immediately. - */ + /* If irq pending already clear it. */ + if (xen_test_irq_pending(irq)) { + xen_clear_irq_pending(irq); + } else if (READ_ONCE(*byte) == val) { + /* Block until irq becomes pending (or a spurious wakeup) */ + xen_poll_irq(irq); + } - /* Block until irq becomes pending (or perhaps a spurious wakeup) */ - xen_poll_irq(irq); + local_irq_restore(flags); } static irqreturn_t dummy_handler(int irq, void *dev_id) |