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| author | Benjamin Herrenschmidt <benh@kernel.crashing.org> | 2013-09-24 09:17:21 +0400 |
|---|---|---|
| committer | Benjamin Herrenschmidt <benh@kernel.crashing.org> | 2013-09-25 08:15:51 +0400 |
| commit | cbc9565ee82694dec31d8137dec975b83175183b (patch) | |
| tree | 7740d7f8f0372e80c067ee2e867bb69ab7b15eec /arch/powerpc/kernel/irq.c | |
| parent | 0366a1c70b89efed4f9d590216bb004a16effbed (diff) | |
| download | linux-cbc9565ee82694dec31d8137dec975b83175183b.tar.xz | |
powerpc: Remove ksp_limit on ppc64
We've been keeping that field in thread_struct for a while, it contains
the "limit" of the current stack pointer and is meant to be used for
detecting stack overflows.
It has a few problems however:
- First, it was never actually *used* on 64-bit. Set and updated but
not actually exploited
- When switching stack to/from irq and softirq stacks, it's update
is racy unless we hard disable interrupts, which is costly. This
is fine on 32-bit as we don't soft-disable there but not on 64-bit.
Thus rather than fixing 2 in order to implement 1 in some hypothetical
future, let's remove the code completely from 64-bit. In order to avoid
a clutter of ifdef's, we remove the updates from C code completely
during interrupt stack switching, and instead maintain it from the
asm helper that is used to do the stack switching in the first place.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Diffstat (limited to 'arch/powerpc/kernel/irq.c')
| -rw-r--r-- | arch/powerpc/kernel/irq.c | 12 |
1 files changed, 0 insertions, 12 deletions
diff --git a/arch/powerpc/kernel/irq.c b/arch/powerpc/kernel/irq.c index 2234a1276a77..57d286a78f86 100644 --- a/arch/powerpc/kernel/irq.c +++ b/arch/powerpc/kernel/irq.c @@ -496,7 +496,6 @@ void do_IRQ(struct pt_regs *regs) { struct pt_regs *old_regs = set_irq_regs(regs); struct thread_info *curtp, *irqtp; - unsigned long saved_sp_limit; /* Switch to the irq stack to handle this */ curtp = current_thread_info(); @@ -509,12 +508,6 @@ void do_IRQ(struct pt_regs *regs) return; } - /* Adjust the stack limit */ - saved_sp_limit = current->thread.ksp_limit; - current->thread.ksp_limit = (unsigned long)irqtp + - _ALIGN_UP(sizeof(struct thread_info), 16); - - /* Prepare the thread_info in the irq stack */ irqtp->task = curtp->task; irqtp->flags = 0; @@ -526,7 +519,6 @@ void do_IRQ(struct pt_regs *regs) call_do_irq(regs, irqtp); /* Restore stack limit */ - current->thread.ksp_limit = saved_sp_limit; irqtp->task = NULL; /* Copy back updates to the thread_info */ @@ -604,16 +596,12 @@ void irq_ctx_init(void) static inline void do_softirq_onstack(void) { struct thread_info *curtp, *irqtp; - unsigned long saved_sp_limit = current->thread.ksp_limit; curtp = current_thread_info(); irqtp = softirq_ctx[smp_processor_id()]; irqtp->task = curtp->task; irqtp->flags = 0; - current->thread.ksp_limit = (unsigned long)irqtp + - _ALIGN_UP(sizeof(struct thread_info), 16); call_do_softirq(irqtp); - current->thread.ksp_limit = saved_sp_limit; irqtp->task = NULL; /* Set any flag that may have been set on the |