diff options
| author | Linus Torvalds <torvalds@linux-foundation.org> | 2012-02-19 11:46:36 -0800 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2012-02-20 09:30:18 +0100 |
| commit | 986cb48c5a4de0085db94d343b4e7dcf54355ec1 (patch) | |
| tree | a25140de28f6b73dca92600273f589719af090b3 | |
| parent | b01543dfe67bb1d191998e90d20534dc354de059 (diff) | |
x86-32/irq: Don't switch to irq stack for a user-mode irq
If the irq happens in user mode, our kernel stack is empty
(apart from the pt_regs themselves, of course), so there's no
need or advantage to switch.
And it really doesn't save any stack space, quite the reverse:
it means that a nested interrupt cannot switch irq stacks. So
instead of saving kernel stack space, it actually causes the
potential for *more* stack usage.
Also simplify the preemption count copy when we do switch
stacks: just copy the whole preemption count, rather than just
the softirq parts of it. There is no advantage to the partial
copy: it is more effort to get a less correct result.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/alpine.LFD.2.02.1202191139260.10000@i5.linux-foundation.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
| -rw-r--r-- | arch/x86/kernel/irq_32.c | 11 |
1 files changed, 3 insertions, 8 deletions
diff --git a/arch/x86/kernel/irq_32.c b/arch/x86/kernel/irq_32.c index 40fc86161d92..58b7f27cb3e9 100644 --- a/arch/x86/kernel/irq_32.c +++ b/arch/x86/kernel/irq_32.c @@ -100,13 +100,8 @@ execute_on_irq_stack(int overflow, struct irq_desc *desc, int irq) irqctx->tinfo.task = curctx->tinfo.task; irqctx->tinfo.previous_esp = current_stack_pointer; - /* - * Copy the softirq bits in preempt_count so that the - * softirq checks work in the hardirq context. - */ - irqctx->tinfo.preempt_count = - (irqctx->tinfo.preempt_count & ~SOFTIRQ_MASK) | - (curctx->tinfo.preempt_count & SOFTIRQ_MASK); + /* Copy the preempt_count so that the [soft]irq checks work. */ + irqctx->tinfo.preempt_count = curctx->tinfo.preempt_count; if (unlikely(overflow)) call_on_stack(print_stack_overflow, isp); @@ -196,7 +191,7 @@ bool handle_irq(unsigned irq, struct pt_regs *regs) if (unlikely(!desc)) return false; - if (!execute_on_irq_stack(overflow, desc, irq)) { + if (user_mode_vm(regs) || !execute_on_irq_stack(overflow, desc, irq)) { if (unlikely(overflow)) print_stack_overflow(); desc->handle_irq(irq, desc); |