do_work_pending: Enable interrupts in do_work_pending()
PATCH 1/1 do_work_pending: Enable interrupts in do_work_pending()
A recent change triggered a WARN_ON that interrupts were disabled, and in fact other architectures enable interrupts uniformly for their related do_work_pending() type code, and all the things we call from this routine appear to expect interrupts to be enabled. So, enable them. Below is the warning.
[ 12.094106] systemd-udevd[1643]: starting version 204 [ 13.466537] ------------[ cut here ]------------ [ 13.469750] WARNING: CPU: 1 PID: 1645 at kernel/locking/lockdep.c:3536 check_flags+0x7c/0x1d0() [ 13.478397] DEBUG_LOCKS_WARN_ON(current->hardirqs_enabled) [ 13.483663] Modules linked in: [ 13.486863] CPU: 1 PID: 1645 Comm: systemd-udevd Not tainted 3.17.4-arm7 #6 [ 13.493851] [<c0013dc8>] (unwind_backtrace) from [<c0011208>] (show_stack+0x10/0x14) [ 13.501563] [<c0011208>] (show_stack) from [<c05df5f0>] (dump_stack+0x80/0xac) [ 13.508753] [<c05df5f0>] (dump_stack) from [<c0024594>] (warn_slowpath_common+0x60/0x84) [ 13.516808] [<c0024594>] (warn_slowpath_common) from [<c00245e4>] (warn_slowpath_fmt+0x2c/0x3c) [ 13.525463] [<c00245e4>] (warn_slowpath_fmt) from [<c006c508>] (check_flags+0x7c/0x1d0) [ 13.533447] [<c006c508>] (check_flags) from [<c006cf60>] (lock_is_held+0x34/0x60) [ 13.540884] [<c006cf60>] (lock_is_held) from [<c05e0500>] (__schedule+0x98/0x7cc) [ 13.548342] [<c05e0500>] (__schedule) from [<c0010adc>] (do_work_pending+0x28/0xbc) [ 13.555962] [<c0010adc>] (do_work_pending) from [<c000dd38>] (work_pending+0xc/0x20) [ 13.563663] ---[ end trace 33bbfa4173cfa520 ]--- [ 13.568238] possible reason: unannotated irqs-off. [ 13.573005] irq event stamp: 5227 [ 13.576293] hardirqs last enabled at (5227): [<c000dd04>] ret_fast_syscall+0x24/0x48 [ 13.584096] hardirqs last disabled at (5226): [<c000dcec>] ret_fast_syscall+0xc/0x48 [ 13.591823] softirqs last enabled at (5222): [<c00283b0>] __do_softirq+0x1e8/0x270 [ 13.599447] softirqs last disabled at (5205): [<c00286f4>] irq_exit+0x84/0xf4 [ 13.656634] random: nonblocking pool is initialized
--- arch/arm/kernel/signal.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-)
arch/arm/kernel/signal.c +7 -4
@@ -476,7 +476,7 @@ setup_rt_frame(struct ksignal *ksig, sigset_t *set, struct pt_regs *regs)/* * OK, we're invoking a handler -*/ +*/ static void handle_signal (struct ksignal *ksig,struct pt_regs *regs) {sigset_t *oldset =sigmask_to_save ();
@@ -574,12 +574,14 @@ asmlinkage int do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall) { do { + if (unlikely(!user_mode(regs))) + return 0; + /* Enable interrupts; they are disabled again on return to + * caller. */ + local_irq_enable(); if (likely(thread_flags & _TIF_NEED_RESCHED)) {schedule (); } else { -if (unlikely (!user_mode (regs))) -return 0 ; -local_irq_enable ();if (thread_flags & _TIF_SIGPENDING) {int restart =do_signal (regs, syscall);if (unlikely (restart)) {
@@ -588,6 +590,7 @@ do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)* Deal with it without leaving * the kernel space. */ +local_irq_disable ();return restart; } syscall =0 ;
Signature · 1 line
2.1.0
Quoted 8 lines · Anand Moon
arch/arm/kernel/signal.c +4
-0@@ -574,12 +574,14 @@ asmlinkage int do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall) { do { + if (unlikely(!user_mode(regs))) + return 0; + /* Enable interrupts; they are disabled again on return to + * caller. */
arch/arm/kernel/signal.c asmlinkage int · line 587
Quoted 10 lines
arch/arm/kernel/signal.c +1
-3+local_irq_enable ();if (likely (thread_flags & _TIF_NEED_RESCHED)) {schedule (); }else { -if (unlikely (!user_mode (regs))) -return 0 ; -local_irq_enable ();if (thread_flags & _TIF_SIGPENDING) {int restart =do_signal (regs, syscall);if (unlikely (restart)) {
I'm happy with the hunk above, but:
arch/arm/kernel/signal.c do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall) · line 594
Quoted 6 lines
arch/arm/kernel/signal.c +1
-0@@ -588,6 +590,7 @@ do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)* Deal with it without leaving * the kernel space. */ +local_irq_disable ();return restart;
not this one. The code expects in the non-zero return case, that interrupts will be enabled, otherwise we will be restarting the syscall with IRQs disabled, and calling into the syscall function with IRQs disabled.
Signature · 2 lines
FTTC broadband for 0.8mile line: currently at 9.5Mbps down 400kbps up according to speedtest.net.
PATCH 1/1 do_work_pending: Enable interrupts in do_work_pending()
hi Russell King,
I was experiencing the same problem. You mention.
I realized later after few application failure an system slowdown.
-Anand Moon
Quoted 32 lines · Russell King - ARM Linux
Quoted 8 lines · Anand Moon
arch/arm/kernel/signal.c +4
-0@@ -574,12 +574,14 @@ asmlinkage int do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall) { do { + if (unlikely(!user_mode(regs))) + return 0; + /* Enable interrupts; they are disabled again on return to + * caller. */arch/arm/kernel/signal.c asmlinkage int · line 587
Quoted 10 lines
arch/arm/kernel/signal.c +1
-3+local_irq_enable ();if (likely (thread_flags & _TIF_NEED_RESCHED)) {schedule (); }else { -if (unlikely (!user_mode (regs))) -return 0 ; -local_irq_enable ();if (thread_flags & _TIF_SIGPENDING) {int restart =do_signal (regs, syscall);if (unlikely (restart)) {I'm happy with the hunk above, but:
arch/arm/kernel/signal.c do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall) · line 594
Quoted 6 lines
arch/arm/kernel/signal.c +1
-0@@ -588,6 +590,7 @@ do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall)* Deal with it without leaving * the kernel space. */ +local_irq_disable ();return restart;not this one. The code expects in the non-zero return case, that interrupts will be enabled, otherwise we will be restarting the syscall with IRQs disabled, and calling into the syscall function with IRQs disabled.