From: Michael Ellerman <patch-notifications@ellerman.id.au>
To: Nicholas Piggin <npiggin@gmail.com>, linuxppc-dev@lists.ozlabs.org
Cc: Nicholas Piggin <npiggin@gmail.com>
Subject: Re: [PATCH] powerpc/64: Don't trace code that runs with the soft irq mask unreconciled
Date: Fri, 3 May 2019 16:59:29 +1000 (AEST) [thread overview]
Message-ID: <44wNKY504cz9sPZ@ozlabs.org> (raw)
In-Reply-To: <20190502052107.24738-1-npiggin@gmail.com>
On Thu, 2019-05-02 at 05:21:07 UTC, Nicholas Piggin wrote:
> "Reconciling" in terms of interrupt handling, is to bring the soft irq
> mask state in to synch with the hardware, after an interrupt causes
> MSR[EE] to be cleared (while the soft mask may be enabled, and hard
> irqs not marked disabled).
>
> General kernel code should not be called while unreconciled, because
> local_irq_disable, etc. manipulations can cause surprising irq traces,
> and it's fragile because the soft irq code does not really expect to
> be called in this situation.
>
> When exiting from an interrupt, MSR[EE] is cleared to prevent races,
> but soft irq state is enabled for the returned-to context, so this is
> now an unreconciled state. restore_math is called in this state, and
> that can be ftraced, and the ftrace subsystem disables local irqs.
>
> Mark restore_math and its callees as notrace. Restore a sanity check
> in the soft irq code that had to be disabled for this case, by commit
> 4da1f79227ad4 ("powerpc/64: Disable irq restore warning for now").
>
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Applied to powerpc next, thanks.
https://git.kernel.org/powerpc/c/e2b36d591720d81741f37e047a6f0047
cheers
prev parent reply other threads:[~2019-05-03 7:54 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-02 5:21 [PATCH] powerpc/64: Don't trace code that runs with the soft irq mask unreconciled Nicholas Piggin
2019-05-03 6:59 ` Michael Ellerman [this message]
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