From: Peter Zijlstra <peterz@infradead.org>
To: Rik van Riel <riel@surriel.com>
Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com,
will.deacon@arm.com, songliubraving@fb.com, mingo@kernel.org,
luto@kernel.org, hpa@zytor.com, npiggin@gmail.com,
Linus Torvalds <torvalds@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
efault@gmx.de
Subject: Re: [PATCH 2/7] x86/mm/tlb: Restructure switch_mm_irqs_off()
Date: Tue, 2 Oct 2018 09:32:54 +0200 [thread overview]
Message-ID: <20181002073254.GP3439@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20180926035844.1420-3-riel@surriel.com>
On Tue, Sep 25, 2018 at 11:58:39PM -0400, Rik van Riel wrote:
> Move some code that will be needed for the lazy -> !lazy state
> transition when a lazy TLB CPU has gotten out of date.
>
> No functional changes, since the if (real_prev == next) branch
> always returns.
>
> Suggested-by: Andy Lutomirski <luto@kernel.org>
> Signed-off-by: Rik van Riel <riel@surriel.com>
> Acked-by: Dave Hansen <dave.hansen@intel.com>
> Cc: Linus Torvalds <torvalds@linux-foundation.org>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: efault@gmx.de
> Cc: kernel-team@fb.com
> Link: http://lkml.kernel.org/r/20180716190337.26133-4-riel@surriel.com
> Signed-off-by: Ingo Molnar <mingo@kernel.org>
> (cherry picked from commit 61d0beb5796ab11f7f3bf38cb2eccc6579aaa70b)
> ---
> arch/x86/mm/tlb.c | 64 ++++++++++++++++++++++++-----------------------
> 1 file changed, 33 insertions(+), 31 deletions(-)
>
> diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
> index 54a5870190a6..1224f7fb1311 100644
> --- a/arch/x86/mm/tlb.c
> +++ b/arch/x86/mm/tlb.c
> @@ -187,6 +187,8 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
> u16 prev_asid = this_cpu_read(cpu_tlbstate.loaded_mm_asid);
> unsigned cpu = smp_processor_id();
> u64 next_tlb_gen;
> + bool need_flush;
> + u16 new_asid;
>
> /*
> * NB: The scheduler will call us with prev == next when switching
> @@ -308,44 +310,44 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
> /* Let nmi_uaccess_okay() know that we're changing CR3. */
> this_cpu_write(cpu_tlbstate.loaded_mm, LOADED_MM_SWITCHING);
> barrier();
> + }
Compiling this gives me:
CC arch/x86/mm/tlb.o
../arch/x86/mm/tlb.c: In function ‘switch_mm_irqs_off’:
../arch/x86/mm/tlb.c:315:5: warning: ‘need_flush’ may be used uninitialized in this function [-Wmaybe-uninitialized]
if (need_flush) {
^
../arch/x86/mm/tlb.c:316:45: warning: ‘new_asid’ may be used uninitialized in this function [-Wmaybe-uninitialized]
this_cpu_write(cpu_tlbstate.ctxs[new_asid].ctx_id, next->context.ctx_id);
^
Because you shadow need_flush and new_asid in a branch. I need the below
delta to make it happy again.
---
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -254,8 +254,6 @@ void switch_mm_irqs_off(struct mm_struct
return;
} else {
- u16 new_asid;
- bool need_flush;
u64 last_ctx_id = this_cpu_read(cpu_tlbstate.last_ctx_id);
/*
next prev parent reply other threads:[~2018-10-02 7:33 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-26 3:58 [PATCH v2 0/7] x86/mm/tlb: make lazy TLB mode even lazier Rik van Riel
2018-09-26 3:58 ` [PATCH 1/7] x86/mm/tlb: Always use lazy TLB mode Rik van Riel
2018-10-01 15:58 ` Peter Zijlstra
2018-10-01 16:07 ` Rik van Riel
2018-09-26 3:58 ` [PATCH 2/7] x86/mm/tlb: Restructure switch_mm_irqs_off() Rik van Riel
2018-10-02 7:32 ` Peter Zijlstra [this message]
2018-09-26 3:58 ` [PATCH 3/7] smp: use __cpumask_set_cpu in on_each_cpu_cond Rik van Riel
2018-10-09 14:59 ` [tip:x86/mm] " tip-bot for Rik van Riel
2018-09-26 3:58 ` [PATCH 4/7] smp,cpumask: introduce on_each_cpu_cond_mask Rik van Riel
2018-10-09 14:59 ` [tip:x86/mm] " tip-bot for Rik van Riel
2018-09-26 3:58 ` [PATCH 5/7] Add freed_tables argument to flush_tlb_mm_range Rik van Riel
2018-10-09 15:00 ` [tip:x86/mm] x86/mm/tlb: " tip-bot for Rik van Riel
2018-09-26 3:58 ` [PATCH 6/7] Add freed_tables element to flush_tlb_info Rik van Riel
2018-10-09 15:00 ` [tip:x86/mm] x86/mm/tlb: " tip-bot for Rik van Riel
2018-09-26 3:58 ` [PATCH 7/7] x86/mm/tlb: Make lazy TLB mode lazier Rik van Riel
2018-10-01 16:07 ` Peter Zijlstra
2018-10-09 15:01 ` [tip:x86/mm] " tip-bot for Rik van Riel
2018-10-01 16:09 ` [PATCH v2 0/7] x86/mm/tlb: make lazy TLB mode even lazier Peter Zijlstra
2018-10-02 7:44 ` Peter Zijlstra
2018-10-02 13:41 ` Rik van Riel
-- strict thread matches above, loose matches on Subject: below --
2018-09-24 18:37 [PATCH " Rik van Riel
2018-09-24 18:37 ` [PATCH 2/7] x86/mm/tlb: Restructure switch_mm_irqs_off() Rik van Riel
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