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metag: kick: add missing irq_enter/exit to kick_handler()

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kick_handler() doesn't have an irq_enter/exit pair, but it's used for
handling SMP IPIs which require work to be done in softirqs, which are
invoked from irq_exit() when the hard irq nest count reaches 0.

The scheduler_ipi() callback in the IPI handler calls irq_enter/exit
itself, but this is inside kick_handler()'s spin lock critical section,
so if an invoked softirq issues an IPI the kick_handler() will be
re-entered on the same CPU and will deadlock.

This is easily fixed by adding the missing irq_enter/exit to
kick_handler() so that the hard irq nest count doesn't reach 0 until
after the spin lock has been released.

Ideally the spin lock protected handler list will also be replaced by a
lockless RCU protected list since it is certainly mostly read. That can
be done in a later change though.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
James Hogan 2013-07-01 13:44:10 +01:00
parent 9649814432
commit f6b30d32d2
1 changed files with 9 additions and 0 deletions
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9
arch/metag/kernel/kick.c
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@ -26,6 +26,8 @@
* pass it as an argument. * pass it as an argument.
*/ */
#include <linux/export.h> #include <linux/export.h>
#include <linux/hardirq.h>
#include <linux/irq.h>
#include <linux/kernel.h> #include <linux/kernel.h>
#include <linux/mm.h> #include <linux/mm.h>
#include <linux/types.h> #include <linux/types.h>
@ -66,6 +68,7 @@ EXPORT_SYMBOL(kick_unregister_func);
TBIRES TBIRES
kick_handler(TBIRES State, int SigNum, int Triggers, int Inst, PTBI pTBI) kick_handler(TBIRES State, int SigNum, int Triggers, int Inst, PTBI pTBI)
{ {
struct pt_regs *old_regs;
struct kick_irq_handler *kh; struct kick_irq_handler *kh;
struct list_head *lh; struct list_head *lh;
int handled = 0; int handled = 0;
@ -79,6 +82,9 @@ kick_handler(TBIRES State, int SigNum, int Triggers, int Inst, PTBI pTBI)
trace_hardirqs_off(); trace_hardirqs_off();
old_regs = set_irq_regs((struct pt_regs *)State.Sig.pCtx);
irq_enter();
/* /*
* There is no need to disable interrupts here because we * There is no need to disable interrupts here because we
* can't nest KICK interrupts in a KICK interrupt handler. * can't nest KICK interrupts in a KICK interrupt handler.
@ -97,5 +103,8 @@ kick_handler(TBIRES State, int SigNum, int Triggers, int Inst, PTBI pTBI)
WARN_ON(!handled); WARN_ON(!handled);
irq_exit();
set_irq_regs(old_regs);
return tail_end(ret); return tail_end(ret);
} }