From: Yinghai Lu <[email protected]> check_irq_vectors_for_cpu_disable() may overestimate the number of available vectors assigned to a cpu. This can cause cpu remove to erroneously fail.
commit da6139e49c7cb0f4251265cb5243b8d220adb48d, x86: Add check for number of available vectors before CPU down, introduces a check to see if there are enough empty vectors in the system to replace a downed cpu's vectors. Code inspection shows that the range used in the check (currently from FIRST_EXTERNAL_VECTOR to NR_VECTORS) is incorrect and should be FIRST_EXTERNAL_VECTOR to first_system_vector. The value of first_system_vector is decremented when system vectors are assigned in alloc_system_vector(). The check_irq_vectors_for_cpu_disable() check also does not take into account the first 32 system vectors which are not managed in the per_cpu vector_irq arrays, including IA32_SYSCALL_VECTOR (0x80) and the IRQ_MOVE_CLEANUP_VECTOR (0x20). Cc: Thomas Gleixner <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: "H. Peter Anvin" <[email protected]> Cc: [email protected] Cc: Seiji Aguchi <[email protected]> Cc: Andi Kleen <[email protected]> Cc: "K. Y. Srinivasan" <[email protected]> Cc: "Steven Rostedt (Red Hat)" <[email protected]> Cc: Yinghai Lu <[email protected]> Acked-by: Prarit Bhargava <[email protected]> Signed-off-by: Yinghai Lu <[email protected]> --- arch/x86/kernel/irq.c | 21 ++++++++++++++++++--- 1 file changed, 18 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c index 283a76a..d03ff8f 100644 --- a/arch/x86/kernel/irq.c +++ b/arch/x86/kernel/irq.c @@ -17,6 +17,7 @@ #include <asm/idle.h> #include <asm/mce.h> #include <asm/hw_irq.h> +#include <asm/desc.h> #define CREATE_TRACE_POINTS #include <asm/trace/irq_vectors.h> @@ -334,10 +335,24 @@ int check_irq_vectors_for_cpu_disable(void) for_each_online_cpu(cpu) { if (cpu == this_cpu) continue; - for (vector = FIRST_EXTERNAL_VECTOR; vector < NR_VECTORS; - vector++) { - if (per_cpu(vector_irq, cpu)[vector] < 0) + + /* + * assign_irq_vector() only scan per_cpu vectors from + * FIRST_EXTERNAL_VECTOR to first_system_vector. + * It aslo skip vectors that are set in used_vectors bitmask. + * used_vectors could have bits set for + * IA32_SYSCALL_VECTOR (0x80) + * IRQ_MOVE_CLEANUP_VECTOR (0x20) + * Don't count those as available vectors. + */ + for (vector = FIRST_EXTERNAL_VECTOR; + vector < first_system_vector; vector++) { + if (test_bit(vector, used_vectors)) + continue; + + if (per_cpu(vector_irq, cpu)[vector] < 0) { count++; + } } } -- 1.7.9.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
