Messages in this thread | | | Date | Wed, 8 Mar 2023 14:34:36 +0100 | Subject | Re: [PATCH] ACPI: PPTT: Fix to avoid sleep in the atomic context when PPTT is absent | From | Pierre Gondois <> |
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Tested-by: Pierre Gondois <pierre.gondois@arm.com>
On 3/8/23 12:26, Sudeep Holla wrote: > Commit 0c80f9e165f8 ("ACPI: PPTT: Leave the table mapped for the runtime usage") > enabled to map PPTT once on the first invocation of acpi_get_pptt() and > never unmapped the same allowing it to be used at runtime with out the > hassle of mapping and unmapping the table. This was needed to fetch LLC > information from the PPTT in the cpuhotplug path which is executed in > the atomic context as the acpi_get_table() might sleep waiting for a > mutex. > > However it missed to handle the case when there is no PPTT on the system > which results in acpi_get_pptt() being called from all the secondary > CPUs attempting to fetch the LLC information in the atomic context > without knowing the absence of PPTT resulting in the splat like below: > > | BUG: sleeping function called from invalid context at kernel/locking/semaphore.c:164 > | in_atomic(): 1, irqs_disabled(): 1, non_block: 0, pid: 0, name: swapper/1 > | preempt_count: 1, expected: 0 > | RCU nest depth: 0, expected: 0 > | no locks held by swapper/1/0. > | irq event stamp: 0 > | hardirqs last enabled at (0): 0x0 > | hardirqs last disabled at (0): copy_process+0x61c/0x1b40 > | softirqs last enabled at (0): copy_process+0x61c/0x1b40 > | softirqs last disabled at (0): 0x0 > | CPU: 1 PID: 0 Comm: swapper/1 Not tainted 6.3.0-rc1 #1 > | Call trace: > | dump_backtrace+0xac/0x138 > | show_stack+0x30/0x48 > | dump_stack_lvl+0x60/0xb0 > | dump_stack+0x18/0x28 > | __might_resched+0x160/0x270 > | __might_sleep+0x58/0xb0 > | down_timeout+0x34/0x98 > | acpi_os_wait_semaphore+0x7c/0xc0 > | acpi_ut_acquire_mutex+0x58/0x108 > | acpi_get_table+0x40/0xe8 > | acpi_get_pptt+0x48/0xa0 > | acpi_get_cache_info+0x38/0x140 > | init_cache_level+0xf4/0x118 > | detect_cache_attributes+0x2e4/0x640 > | update_siblings_masks+0x3c/0x330 > | store_cpu_topology+0x88/0xf0 > | secondary_start_kernel+0xd0/0x168 > | __secondary_switched+0xb8/0xc0 > > Update acpi_get_pptt() to consider the fact that PPTT is once checked and > is not available on the system and return NULL avoiding any attempts to > fetch PPTT and thereby avoiding any possible sleep waiting for a mutex > in the atomic context. > > Fixes: 0c80f9e165f8 ("ACPI: PPTT: Leave the table mapped for the runtime usage") > Reported-by: Aishwarya TCV <aishwarya.tcv@arm.com> > Cc: Pierre Gondois <pierre.gondois@arm.com> > Signed-off-by: Sudeep Holla <sudeep.holla@arm.com> > --- > drivers/acpi/pptt.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/drivers/acpi/pptt.c b/drivers/acpi/pptt.c > index 10975bb603fb..a35dd0e41c27 100644 > --- a/drivers/acpi/pptt.c > +++ b/drivers/acpi/pptt.c > @@ -536,16 +536,19 @@ static int topology_get_acpi_cpu_tag(struct acpi_table_header *table, > static struct acpi_table_header *acpi_get_pptt(void) > { > static struct acpi_table_header *pptt; > + static bool is_pptt_checked; > acpi_status status; > > /* > * PPTT will be used at runtime on every CPU hotplug in path, so we > * don't need to call acpi_put_table() to release the table mapping. > */ > - if (!pptt) { > + if (!pptt && !is_pptt_checked) { > status = acpi_get_table(ACPI_SIG_PPTT, 0, &pptt); > if (ACPI_FAILURE(status)) > acpi_pptt_warn_missing(); > + > + is_pptt_checked = true; > } > > return pptt;
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