From: Kees Cook <keescook@chromium.org>
To: Jann Horn <jannh@google.com>, Anton Vorontsov <anton@enomsg.org>,
Colin Cross <ccross@android.com>, Tony Luck <tony.luck@intel.com>,
Ard Biesheuvel <ardb@kernel.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org,
stable@vger.kernel.org
Subject: Re: [PATCH v2] pstore: Don't use semaphores in always-atomic-context code
Date: Tue, 22 Feb 2022 23:49:54 -0800 [thread overview]
Message-ID: <8D85619E-99BD-4DB5-BDDB-A205B057C910@chromium.org> (raw)
In-Reply-To: <20220218181950.1438236-1-jannh@google.com>
On February 18, 2022 10:19:50 AM PST, Jann Horn <jannh@google.com> wrote:
>pstore_dump() is *always* invoked in atomic context (nowadays in an RCU
>read-side critical section, before that under a spinlock).
>It doesn't make sense to try to use semaphores here.
Ah, very nice. Thanks for the analysis!
>[...]
>-static bool pstore_cannot_wait(enum kmsg_dump_reason reason)
>+bool pstore_cannot_block_path(enum kmsg_dump_reason reason)
Why the rename, extern, and EXPORT? This appears to still only have the same single caller?
> [...]
>- pr_err("dump skipped in %s path: may corrupt error record\n",
>- in_nmi() ? "NMI" : why);
>- return;
>- }
>- if (down_interruptible(&psinfo->buf_lock)) {
>- pr_err("could not grab semaphore?!\n");
>+ if (pstore_cannot_block_path(reason)) {
>+ if (!spin_trylock_irqsave(&psinfo->buf_lock, flags)) {
>+ pr_err("dump skipped in %s path because of concurrent dump\n"
>+ , in_nmi() ? "NMI" : why);
The pr_err had the comma following the format string moved, and the note about corruption removed. Is that no longer accurate?
Otherwise looks good; thank you!
--
Kees Cook
next prev parent reply other threads:[~2022-02-23 7:50 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-18 18:19 [PATCH v2] pstore: Don't use semaphores in always-atomic-context code Jann Horn
2022-02-23 7:49 ` Kees Cook [this message]
2022-02-23 17:50 ` Jann Horn
2022-02-23 19:29 ` Kees Cook
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