lkml.org 
[lkml]   [2020]   [May]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: [patch V4 part 5 07/31] x86/entry: Provide idtentry_entry/exit_cond_rcu()
    From
    Date

    On 5/5/20 3:53 PM, Thomas Gleixner wrote:
    > The pagefault handler cannot use the regular idtentry_enter() because on
    > that invokes rcu_irq_enter() the pagefault was caused in the kernel.

    I am struggling to understand this part of the sentence: "because on
    that invokes rcu_irq_enter() the pagefault was caused in the kernel."

    Do you mean: "because that invokes rcu_irq_enter() if the pagefault was
    caused in the kernel." ?

    alex.

    > Not a
    > problem per se, but kernel side page faults can schedule which is not
    > possible without invoking rcu_irq_exit().
    >
    > Adding rcu_irq_exit() and a matching rcu_irq_enter() into the actual
    > pagefault handling code is possible, but not pretty either.
    >
    > Provide idtentry_entry/exit_cond_rcu() which calls rcu_irq_enter() only
    > when RCU is not watching. While this is not a legit kernel #PF establishing
    > RCU before handling it avoids RCU side effects which might affect
    > debugability.
    >
    > The function is also useful for implementing lightweight scheduler IPI
    > entry handling later.
    >
    > Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    > ---
    > arch/x86/entry/common.c | 119 ++++++++++++++++++++++++++++++++++------
    > arch/x86/include/asm/idtentry.h | 3 +
    > 2 files changed, 106 insertions(+), 16 deletions(-)

    \
     
     \ /
      Last update: 2020-05-11 15:56    [W:3.036 / U:0.492 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site