| Message ID | 1443653944-21885-1-git-send-email-yang.shi@linaro.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, Sep 30, 2015 at 03:59:04PM -0700, Yang Shi wrote: > diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c > index cebf786..eb520d0 100644 > --- a/arch/arm64/kernel/debug-monitors.c > +++ b/arch/arm64/kernel/debug-monitors.c > @@ -292,11 +292,11 @@ static int call_break_hook(struct pt_regs *regs, unsigned int esr) > struct break_hook *hook; > int (*fn)(struct pt_regs *regs, unsigned int esr) = NULL; > > - read_lock(&break_hook_lock); > + rcu_read_lock(); > list_for_each_entry(hook, &break_hook, node) > if ((esr & hook->esr_mask) == hook->esr_val) > fn = hook->fn; > - read_unlock(&break_hook_lock); > + rcu_read_unlock(); > > return fn ? fn(regs, esr) : DBG_HOOK_ERROR; > } That's not enough, you also need list_(add|del)_rcu where the list is modified, together with list_for_each_entry_rcu() here.
On 10/1/2015 8:07 AM, Catalin Marinas wrote: > On Wed, Sep 30, 2015 at 03:59:04PM -0700, Yang Shi wrote: >> diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c >> index cebf786..eb520d0 100644 >> --- a/arch/arm64/kernel/debug-monitors.c >> +++ b/arch/arm64/kernel/debug-monitors.c >> @@ -292,11 +292,11 @@ static int call_break_hook(struct pt_regs *regs, unsigned int esr) >> struct break_hook *hook; >> int (*fn)(struct pt_regs *regs, unsigned int esr) = NULL; >> >> - read_lock(&break_hook_lock); >> + rcu_read_lock(); >> list_for_each_entry(hook, &break_hook, node) >> if ((esr & hook->esr_mask) == hook->esr_val) >> fn = hook->fn; >> - read_unlock(&break_hook_lock); >> + rcu_read_unlock(); >> >> return fn ? fn(regs, esr) : DBG_HOOK_ERROR; >> } > > That's not enough, you also need list_(add|del)_rcu where the list is > modified, together with list_for_each_entry_rcu() here. Thanks for pointing it out. I'm going to prepare v2 with list_(add|del)_rcu. Yang >
diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c index cebf786..eb520d0 100644 --- a/arch/arm64/kernel/debug-monitors.c +++ b/arch/arm64/kernel/debug-monitors.c @@ -292,11 +292,11 @@ static int call_break_hook(struct pt_regs *regs, unsigned int esr) struct break_hook *hook; int (*fn)(struct pt_regs *regs, unsigned int esr) = NULL; - read_lock(&break_hook_lock); + rcu_read_lock(); list_for_each_entry(hook, &break_hook, node) if ((esr & hook->esr_mask) == hook->esr_val) fn = hook->fn; - read_unlock(&break_hook_lock); + rcu_read_unlock(); return fn ? fn(regs, esr) : DBG_HOOK_ERROR; }
BUG: sleeping function called from invalid context at kernel/locking/rtmutex.c:917 in_atomic(): 0, irqs_disabled(): 128, pid: 342, name: perf 1 lock held by perf/342: #0: (break_hook_lock){+.+...}, at: [<ffffffc0000851ac>] call_break_hook+0x34/0xd0 irq event stamp: 62224 hardirqs last enabled at (62223): [<ffffffc00010b7bc>] __call_rcu.constprop.59+0x104/0x270 hardirqs last disabled at (62224): [<ffffffc0000fbe20>] vprintk_emit+0x68/0x640 softirqs last enabled at (0): [<ffffffc000097928>] copy_process.part.8+0x428/0x17f8 softirqs last disabled at (0): [< (null)>] (null) CPU: 0 PID: 342 Comm: perf Not tainted 4.1.6-rt5 #4 Hardware name: linux,dummy-virt (DT) Call trace: [<ffffffc000089968>] dump_backtrace+0x0/0x128 [<ffffffc000089ab0>] show_stack+0x20/0x30 [<ffffffc0007030d0>] dump_stack+0x7c/0xa0 [<ffffffc0000c878c>] ___might_sleep+0x174/0x260 [<ffffffc000708ac8>] __rt_spin_lock+0x28/0x40 [<ffffffc000708db0>] rt_read_lock+0x60/0x80 [<ffffffc0000851a8>] call_break_hook+0x30/0xd0 [<ffffffc000085a70>] brk_handler+0x30/0x98 [<ffffffc000082248>] do_debug_exception+0x50/0xb8 Exception stack(0xffffffc00514fe30 to 0xffffffc00514ff50) fe20: 00000000 00000000 c1594680 0000007f fe40: ffffffff ffffffff 92063940 0000007f 0550dcd8 ffffffc0 00000000 00000000 fe60: 0514fe70 ffffffc0 000be1f8 ffffffc0 0514feb0 ffffffc0 0008948c ffffffc0 fe80: 00000004 00000000 0514fed0 ffffffc0 ffffffff ffffffff 9282a948 0000007f fea0: 00000000 00000000 9282b708 0000007f c1592820 0000007f 00083914 ffffffc0 fec0: 00000000 00000000 00000010 00000000 00000064 00000000 00000001 00000000 fee0: 005101e0 00000000 c1594680 0000007f c1594740 0000007f ffffffd8 ffffff80 ff00: 00000000 00000000 00000000 00000000 c1594770 0000007f c1594770 0000007f ff20: 00665e10 00000000 7f7f7f7f 7f7f7f7f 01010101 01010101 00000000 00000000 ff40: 928e4cc0 0000007f 91ff11e8 0000007f call_break_hook is called in atomic context (hard irq disabled), so replace the sleepable lock to rcu lock. Signed-off-by: Yang Shi <yang.shi@linaro.org> --- arch/arm64/kernel/debug-monitors.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)