From: "Nicholas Piggin" <npiggin@gmail.com>
To: "Nathan Lynch" <nathanl@linux.ibm.com>, <linuxppc-dev@lists.ozlabs.org>
Cc: tyreld@linux.ibm.com, nnac123@linux.ibm.com,
ldufour@linux.ibm.com, ajd@linux.ibm.com
Subject: Re: [PATCH 03/13] powerpc/rtas: avoid device tree lookups in rtas_os_term()
Date: Mon, 28 Nov 2022 12:29:27 +1000 [thread overview]
Message-ID: <CONKPQU112NE.1K5YZVFHQ7XU9@bobo> (raw)
In-Reply-To: <20221118150751.469393-4-nathanl@linux.ibm.com>
On Sat Nov 19, 2022 at 1:07 AM AEST, Nathan Lynch wrote:
> rtas_os_term() is called during panic. Its behavior depends on a
> couple of conditions in the /rtas node of the device tree, the
> traversal of which entails locking and local IRQ state changes. If the
> kernel panics while devtree_lock is held, rtas_os_term() as currently
> written could hang.
Nice.
>
> Instead of discovering the relevant characteristics at panic time,
> cache them in file-static variables at boot. Note the lookup for
> "ibm,extended-os-term" is converted to of_property_read_bool() since
> it is a boolean property, not a RTAS function token.
Small nit, but you could do that at the query site unless you
were going to start using ibm,os-term without the extended
capability.
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
>
> Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
> ---
> arch/powerpc/kernel/rtas.c | 14 +++++++++++---
> 1 file changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
> index c12dd5ed5e00..81e4996012b7 100644
> --- a/arch/powerpc/kernel/rtas.c
> +++ b/arch/powerpc/kernel/rtas.c
> @@ -947,6 +947,8 @@ void __noreturn rtas_halt(void)
>
> /* Must be in the RMO region, so we place it here */
> static char rtas_os_term_buf[2048];
> +static s32 ibm_os_term_token = RTAS_UNKNOWN_SERVICE;
> +static bool ibm_extended_os_term;
>
> void rtas_os_term(char *str)
> {
> @@ -958,14 +960,13 @@ void rtas_os_term(char *str)
> * this property may terminate the partition which we want to avoid
> * since it interferes with panic_timeout.
> */
> - if (RTAS_UNKNOWN_SERVICE == rtas_token("ibm,os-term") ||
> - RTAS_UNKNOWN_SERVICE == rtas_token("ibm,extended-os-term"))
> + if (ibm_os_term_token == RTAS_UNKNOWN_SERVICE || !ibm_extended_os_term)
> return;
>
> snprintf(rtas_os_term_buf, 2048, "OS panic: %s", str);
>
> do {
> - status = rtas_call(rtas_token("ibm,os-term"), 1, 1, NULL,
> + status = rtas_call(ibm_os_term_token, 1, 1, NULL,
> __pa(rtas_os_term_buf));
> } while (rtas_busy_delay(status));
>
> @@ -1335,6 +1336,13 @@ void __init rtas_initialize(void)
> no_entry = of_property_read_u32(rtas.dev, "linux,rtas-entry", &entry);
> rtas.entry = no_entry ? rtas.base : entry;
>
> + /*
> + * Discover these now to avoid device tree lookups in the
> + * panic path.
> + */
> + ibm_os_term_token = rtas_token("ibm,os-term");
> + ibm_extended_os_term = of_property_read_bool(rtas.dev, "ibm,extended-os-term");
> +
> /* If RTAS was found, allocate the RMO buffer for it and look for
> * the stop-self token if any
> */
> --
> 2.37.1
next prev parent reply other threads:[~2022-11-28 2:30 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-18 15:07 [PATCH 00/13] RTAS maintenance Nathan Lynch
2022-11-18 15:07 ` [PATCH 01/13] powerpc/rtas: document rtas_call() Nathan Lynch
2022-11-22 2:46 ` Andrew Donnellan
2022-11-18 15:07 ` [PATCH 02/13] powerpc/rtasd: use correct OF API for event scan rate Nathan Lynch
2022-11-22 2:39 ` Andrew Donnellan
2022-11-18 15:07 ` [PATCH 03/13] powerpc/rtas: avoid device tree lookups in rtas_os_term() Nathan Lynch
2022-11-22 3:03 ` Andrew Donnellan
2022-11-28 18:08 ` Nathan Lynch
2022-11-28 2:29 ` Nicholas Piggin [this message]
2022-11-28 18:26 ` Nathan Lynch
2022-11-29 6:45 ` Nicholas Piggin
2022-11-29 15:37 ` Nathan Lynch
2022-11-18 15:07 ` [PATCH 04/13] powerpc/rtas: avoid scheduling " Nathan Lynch
2022-11-22 3:17 ` Andrew Donnellan
2022-11-28 2:34 ` Nicholas Piggin
2022-11-18 15:07 ` [PATCH 05/13] powerpc/pseries/eeh: use correct API for error log size Nathan Lynch
2022-11-22 3:21 ` Andrew Donnellan
2022-11-28 20:22 ` Nathan Lynch
2022-11-18 15:07 ` [PATCH 06/13] powerpc/rtas: clean up rtas_error_log_max initialization Nathan Lynch
2022-11-22 3:40 ` Andrew Donnellan
2022-11-18 15:07 ` [PATCH 07/13] powerpc/rtas: clean up includes Nathan Lynch
2022-11-22 4:45 ` Andrew Donnellan
2022-11-18 15:07 ` [PATCH 08/13] powerpc/rtas: define pr_fmt and convert printk call sites Nathan Lynch
2022-11-22 4:07 ` Andrew Donnellan
2022-11-18 15:07 ` [PATCH 09/13] powerpc/rtas: mandate RTAS syscall filtering Nathan Lynch
2022-11-22 4:20 ` Andrew Donnellan
2022-11-18 15:07 ` [PATCH 10/13] powerpc/rtas: improve function information lookups Nathan Lynch
2022-11-23 2:51 ` Andrew Donnellan
2022-11-23 19:32 ` Nick Child
2022-11-24 3:28 ` Andrew Donnellan
2022-11-28 21:19 ` Nathan Lynch
2022-11-29 0:08 ` Nathan Lynch
2022-11-29 7:23 ` Andrew Donnellan
2022-11-29 15:33 ` Nathan Lynch
2022-11-23 20:06 ` Nick Child
2022-11-28 21:57 ` Nathan Lynch
2022-11-18 15:07 ` [PATCH 11/13] powerpc/rtas: strengthen do_enter_rtas() type safety, drop inline Nathan Lynch
2022-11-23 3:23 ` Andrew Donnellan
2022-11-28 2:37 ` Nicholas Piggin
2022-11-18 15:07 ` [PATCH 12/13] powerpc/tracing: tracepoints for RTAS entry and exit Nathan Lynch
2022-11-28 2:54 ` Nicholas Piggin
2022-11-18 15:07 ` [PATCH 13/13] powerpc/rtas: place tracepoints in do_enter_rtas() Nathan Lynch
2022-11-28 3:07 ` Nicholas Piggin
2022-11-28 23:44 ` Nathan Lynch
2022-11-29 0:49 ` Michael Ellerman
2022-11-29 20:24 ` Nathan Lynch
2022-11-30 7:43 ` Michael Ellerman
2022-11-29 6:47 ` Nicholas Piggin
2022-12-08 12:40 ` [PATCH 00/13] RTAS maintenance Michael Ellerman
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