On Fri, 2022-11-18 at 09:07 -0600, 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. > > 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. > > Signed-off-by: Nathan Lynch <nath...@linux.ibm.com>
This seems sensible, minor comment below. Reviewed-by: Andrew Donnellan <a...@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; s32 and int are obviously identical, but rtas_token is declared using int, as are the other variables where we cache various tokens. > +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 > */ -- Andrew Donnellan OzLabs, ADL Canberra a...@linux.ibm.com IBM Australia Limited