From: Nathan Lynch nathanl@linux.ibm.com
[ Upstream commit ed2213bfb192ab51f09f12e9b49b5d482c6493f3 ]
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 Signed-off-by: Sasha Levin sashal@kernel.org --- arch/powerpc/kernel/rtas.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-)
diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c index 0b8a858aa847..082b0c9e0c8a 100644 --- a/arch/powerpc/kernel/rtas.c +++ b/arch/powerpc/kernel/rtas.c @@ -875,6 +875,7 @@ 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) { @@ -886,14 +887,13 @@ 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));
@@ -1255,6 +1255,13 @@ 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 */