Tested-by: Pierre Gondois <pierre.gondois@xxxxxxx> 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@xxxxxxx> Cc: Pierre Gondois <pierre.gondois@xxxxxxx> Signed-off-by: Sudeep Holla <sudeep.holla@xxxxxxx> --- 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;
