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powerpc/rtas: avoid device tree lookups in rtas_os_term()

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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.

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 an RTAS function token.

Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
Reviewed-by: Nicholas Piggin <npiggin@gmail.com>
Reviewed-by: Andrew Donnellan <ajd@linux.ibm.com>
[mpe: Incorporate suggested change from Nick]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20221118150751.469393-4-nathanl@linux.ibm.com
This commit is contained in:
Nathan Lynch 2022-11-18 09:07:41 -06:00 committed by Michael Ellerman
parent b10af504a2
commit ed2213bfb1
1 changed files with 10 additions and 3 deletions
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13
arch/powerpc/kernel/rtas.c
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@ -947,6 +947,7 @@ 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;
void rtas_os_term(char *str)
{
@ -958,14 +959,13 @@ 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)
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 +1335,13 @@ 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.
*/
if (of_property_read_bool(rtas.dev, "ibm,extended-os-term"))
ibm_os_term_token = rtas_token("ibm,os-term");
/* If RTAS was found, allocate the RMO buffer for it and look for
* the stop-self token if any
*/