Debugging with breakpoints on arm64 and RT would trigger the following
call trace. When CONFIG_PREEMPT_RT is enabled, spin_locks become mutexes,
and one of these is the spin lock used in signal handling.
BUG: sleeping function called from invalid context at
kernel/locking/rtmutex.c:969
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 17192, name: multi-timer
INFO: lockdep is turned off.
Preemption disabled at:
[<ffffffc01003bbf0>] debug_exception_enter+0x20/0x70
CPU: 1 PID: 17192 Comm: multi-timer Not tainted 5.10.63-rt47-yocto-preempt-rt #1
Hardware name: Freescale S32G274 (DT)
Call trace:
dump_backtrace+0x0/0x1d4
show_stack+0x24/0x30
dump_stack+0xf0/0x13c
___might_sleep+0x17c/0x1f0
rt_spin_lock+0x6c/0x104
force_sig_info_to_task+0x30/0x12c
force_sig_fault+0x58/0x80
arm64_force_sig_fault+0x4c/0x7c
send_user_sigtrap+0x50/0x84
brk_handler+0x40/0x70
do_debug_exception+0x78/0x194
el0_dbg+0x34/0x54
el0_sync_handler+0x110/0x1b0
el0_sync+0x180/0x1c0
Fix potential sleep while atomic in the similar way of
2dbbc3a07009 ("signal/x86: Delay calling signals in atomic")
Define ARCH_RT_DELAYS_SIGNAL_SEND to enable delaying action in
force_sig_info_to_task. Add actual sending action to arm64 specific path.
Link: https://lore.kernel.org/all/[email protected]/
Back ported for 5.10
Signed-off-by: He Zhe <[email protected]>
---
arch/arm64/include/asm/signal.h | 11 +++++++++++
arch/arm64/kernel/signal.c | 8 ++++++++
2 files changed, 19 insertions(+)
create mode 100644 arch/arm64/include/asm/signal.h
diff --git a/arch/arm64/include/asm/signal.h b/arch/arm64/include/asm/signal.h
new file mode 100644
index 000000000000..dea713119b5b
--- /dev/null
+++ b/arch/arm64/include/asm/signal.h
@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ARM64_ASM_SIGNAL_H
+#define __ARM64_ASM_SIGNAL_H
+
+#include <uapi/asm/signal.h>
+
+#if defined(CONFIG_PREEMPT_RT)
+#define ARCH_RT_DELAYS_SIGNAL_SEND
+#endif
+
+#endif
diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
index fe94a3e1f849..10b9ac9988a3 100644
--- a/arch/arm64/kernel/signal.c
+++ b/arch/arm64/kernel/signal.c
@@ -927,6 +927,14 @@ asmlinkage void do_notify_resume(struct pt_regs *regs,
} else {
local_daif_restore(DAIF_PROCCTX);
+#ifdef ARCH_RT_DELAYS_SIGNAL_SEND
+ if (unlikely(current->forced_info.si_signo)) {
+ struct task_struct *t = current;
+ force_sig_info(&t->forced_info);
+ t->forced_info.si_signo = 0;
+ }
+#endif
+
if (thread_flags & _TIF_UPROBE)
uprobe_notify_resume(regs);
--
2.17.1
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