arm64: Use a raw spinlock in __install_bp_hardening_cb()
PATCH 1/1 arm64: Use a raw spinlock in __install_bp_hardening_cb()
__install_bp_hardening_cb() is called via stop_machine() as part of the cpu_enable callback. To force each CPU to take its turn when allocating slots, they take a spinlock.
With the RT patches applied, the spinlock becomes a mutex, and we get warnings about sleeping while in stop_machine():
| [ 0.319176] CPU features: detected: RAS Extension Support | [ 0.319950] BUG: scheduling while atomic: migration/3/36/0x00000002 | [ 0.319955] Modules linked in: | [ 0.319958] Preemption disabled at: | [ 0.319969] [<ffff000008181ae4>] cpu_stopper_thread+0x7c/0x108 | [ 0.319973] CPU: 3 PID: 36 Comm: migration/3 Not tainted 4.19.1-rt3-00250-g330fc2c2a880 #2 | [ 0.319975] Hardware name: linux,dummy-virt (DT) | [ 0.319976] Call trace: | [ 0.319981] dump_backtrace+0x0/0x148 | [ 0.319983] show_stack+0x14/0x20 | [ 0.319987] dump_stack+0x80/0xa4 | [ 0.319989] __schedule_bug+0x94/0xb0 | [ 0.319991] __schedule+0x510/0x560 | [ 0.319992] schedule+0x38/0xe8 | [ 0.319994] rt_spin_lock_slowlock_locked+0xf0/0x278 | [ 0.319996] rt_spin_lock_slowlock+0x5c/0x90 | [ 0.319998] rt_spin_lock+0x54/0x58 | [ 0.320000] enable_smccc_arch_workaround_1+0xdc/0x260 | [ 0.320001] __enable_cpu_capability+0x10/0x20 | [ 0.320003] multi_cpu_stop+0x84/0x108 | [ 0.320004] cpu_stopper_thread+0x84/0x108 | [ 0.320008] smpboot_thread_fn+0x1e8/0x2b0 | [ 0.320009] kthread+0x124/0x128 | [ 0.320010] ret_from_fork+0x10/0x18
Switch this to a raw spinlock, as we know this is only called with IRQs masked.
--- arch/arm64/kernel/cpu_errata.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
arch/arm64/kernel/cpu_errata.c +3 -3
@@ -135,7 +135,7 @@ static void __install_bp_hardening_cb(bp_hardening_cb_t fn,const char *hyp_vecs_start, const char *hyp_vecs_end) { - static DEFINE_SPINLOCK(bp_lock); + static DEFINE_RAW_SPINLOCK(bp_lock);int cpu, slot =-1 ;/*
@@ -147,7 +147,7 @@ static void __install_bp_hardening_cb(bp_hardening_cb_t fn,return ; } -spin_lock (&bp_lock); +raw_spin_lock (&bp_lock);for_each_possible_cpu (cpu) {if (per_cpu (bp_hardening_data.fn, cpu) == fn) { slot =per_cpu (bp_hardening_data.hyp_vectors_slot, cpu);
@@ -163,7 +163,7 @@ static void __install_bp_hardening_cb(bp_hardening_cb_t fn,__this_cpu_write (bp_hardening_data.hyp_vectors_slot, slot);__this_cpu_write (bp_hardening_data.fn, fn); - spin_unlock(&bp_lock); + raw_spin_unlock(&bp_lock); }#else #define __smccc_workaround_1_smc_start NULL
Signature · 1 line
2.19.1
PATCH 1/1 arm64: Use a raw spinlock in __install_bp_hardening_cb()
Quoted 31 lines · James Morse
__install_bp_hardening_cb()is called viastop_machine()as part of thecpu_enablecallback. To force each CPU to take its turn when allocating slots, they take a spinlock.With the RT patches applied, the spinlock becomes a mutex, and we get warnings about sleeping while in
stop_machine():| [ 0.319176] CPU features: detected: RAS Extension Support | [ 0.319950] BUG: scheduling while atomic: migration/3/36/0x00000002 | [ 0.319955] Modules linked in: | [ 0.319958] Preemption disabled at: | [ 0.319969] [<ffff000008181ae4>] cpu_stopper_thread+0x7c/0x108 | [ 0.319973] CPU: 3 PID: 36 Comm: migration/3 Not tainted 4.19.1-rt3-00250-g330fc2c2a880 #2 | [ 0.319975] Hardware name: linux,dummy-virt (DT) | [ 0.319976] Call trace: | [ 0.319981] dump_backtrace+0x0/0x148 | [ 0.319983] show_stack+0x14/0x20 | [ 0.319987] dump_stack+0x80/0xa4 | [ 0.319989] __schedule_bug+0x94/0xb0 | [ 0.319991] __schedule+0x510/0x560 | [ 0.319992] schedule+0x38/0xe8 | [ 0.319994] rt_spin_lock_slowlock_locked+0xf0/0x278 | [ 0.319996] rt_spin_lock_slowlock+0x5c/0x90 | [ 0.319998] rt_spin_lock+0x54/0x58 | [ 0.320000] enable_smccc_arch_workaround_1+0xdc/0x260 | [ 0.320001] __enable_cpu_capability+0x10/0x20 | [ 0.320003] multi_cpu_stop+0x84/0x108 | [ 0.320004] cpu_stopper_thread+0x84/0x108 | [ 0.320008] smpboot_thread_fn+0x1e8/0x2b0 | [ 0.320009] kthread+0x124/0x128 | [ 0.320010] ret_from_fork+0x10/0x18
Quoted 2 lines
Switch this to a raw spinlock, as we know this is only called with IRQs masked.
There might be a lock-free way to do this, but this isn't a fast-path so I've queued up your patch for 4.21.
Thanks!
Will
PATCH 1/1 arm64: Use a raw spinlock in __install_bp_hardening_cb()
In reply to James MorseQuoted 32 lines · James Morse
__install_bp_hardening_cb()is called viastop_machine()as part of thecpu_enablecallback. To force each CPU to take its turn when allocating slots, they take a spinlock.With the RT patches applied, the spinlock becomes a mutex, and we get warnings about sleeping while in
stop_machine():| [ 0.319176] CPU features: detected: RAS Extension Support | [ 0.319950] BUG: scheduling while atomic: migration/3/36/0x00000002 | [ 0.319955] Modules linked in: | [ 0.319958] Preemption disabled at: | [ 0.319969] [<ffff000008181ae4>] cpu_stopper_thread+0x7c/0x108 | [ 0.319973] CPU: 3 PID: 36 Comm: migration/3 Not tainted 4.19.1-rt3-00250-g330fc2c2a880 #2 | [ 0.319975] Hardware name: linux,dummy-virt (DT) | [ 0.319976] Call trace: | [ 0.319981] dump_backtrace+0x0/0x148 | [ 0.319983] show_stack+0x14/0x20 | [ 0.319987] dump_stack+0x80/0xa4 | [ 0.319989] __schedule_bug+0x94/0xb0 | [ 0.319991] __schedule+0x510/0x560 | [ 0.319992] schedule+0x38/0xe8 | [ 0.319994] rt_spin_lock_slowlock_locked+0xf0/0x278 | [ 0.319996] rt_spin_lock_slowlock+0x5c/0x90 | [ 0.319998] rt_spin_lock+0x54/0x58 | [ 0.320000] enable_smccc_arch_workaround_1+0xdc/0x260 | [ 0.320001] __enable_cpu_capability+0x10/0x20 | [ 0.320003] multi_cpu_stop+0x84/0x108 | [ 0.320004] cpu_stopper_thread+0x84/0x108 | [ 0.320008] smpboot_thread_fn+0x1e8/0x2b0 | [ 0.320009] kthread+0x124/0x128 | [ 0.320010] ret_from_fork+0x10/0x18
Quoted 4 lines
Switch this to a raw spinlock, as we know this is only called with IRQs masked.
Signed-off-by James Morse <[email protected]>
M.
Signature · 1 line
Jazz is not dead, it just smell funny.