lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Fri, 14 Feb 2014 13:25:29 +0530 From: "Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com> To: paulus@...ba.org, oleg@...hat.com, mingo@...nel.org, rusty@...tcorp.com.au, peterz@...radead.org, tglx@...utronix.de, akpm@...ux-foundation.org Cc: paulmck@...ux.vnet.ibm.com, tj@...nel.org, walken@...gle.com, ego@...ux.vnet.ibm.com, linux@....linux.org.uk, rjw@...ysocki.net, linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org, srivatsa.bhat@...ux.vnet.ibm.com, Robert Richter <rric@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...nel.org>, "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org, "Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com> Subject: [PATCH v2 28/52] x86, oprofile, nmi: Fix CPU hotplug callback registration Subsystems that want to register CPU hotplug callbacks, as well as perform initialization for the CPUs that are already online, often do it as shown below: get_online_cpus(); for_each_online_cpu(cpu) init_cpu(cpu); register_cpu_notifier(&foobar_cpu_notifier); put_online_cpus(); This is wrong, since it is prone to ABBA deadlocks involving the cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently with CPU hotplug operations). Instead, the correct and race-free way of performing the callback registration is: cpu_notifier_register_begin(); for_each_online_cpu(cpu) init_cpu(cpu); /* Note the use of the double underscored version of the API */ __register_cpu_notifier(&foobar_cpu_notifier); cpu_notifier_register_done(); Fix the oprofile code in x86 by using this latter form of callback registration. But retain the calls to get/put_online_cpus(), since they are used in other places as well, to protect the variables 'nmi_enabled' and 'ctr_running'. Strictly speaking, this is not necessary since cpu_notifier_register_begin/done() provide a stronger synchronization with CPU hotplug than get/put_online_cpus(). However, let's retain the calls to get/put_online_cpus() to be consistent with the other call-sites. By nesting get/put_online_cpus() *inside* cpu_notifier_register_begin/done(), we avoid the ABBA deadlock possibility mentioned above. Cc: Robert Richter <rric@...nel.org> Cc: Thomas Gleixner <tglx@...utronix.de> Cc: Ingo Molnar <mingo@...nel.org> Cc: "H. Peter Anvin" <hpa@...or.com> Cc: x86@...nel.org Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com> --- arch/x86/oprofile/nmi_int.c | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/arch/x86/oprofile/nmi_int.c b/arch/x86/oprofile/nmi_int.c index 6890d84..379e8bd 100644 --- a/arch/x86/oprofile/nmi_int.c +++ b/arch/x86/oprofile/nmi_int.c @@ -494,14 +494,19 @@ static int nmi_setup(void) if (err) goto fail; + cpu_notifier_register_begin(); + + /* Use get/put_online_cpus() to protect 'nmi_enabled' */ get_online_cpus(); - register_cpu_notifier(&oprofile_cpu_nb); nmi_enabled = 1; /* make nmi_enabled visible to the nmi handler: */ smp_mb(); on_each_cpu(nmi_cpu_setup, NULL, 1); + __register_cpu_notifier(&oprofile_cpu_nb); put_online_cpus(); + cpu_notifier_register_done(); + return 0; fail: free_msrs(); @@ -512,12 +517,18 @@ static void nmi_shutdown(void) { struct op_msrs *msrs; + cpu_notifier_register_begin(); + + /* Use get/put_online_cpus() to protect 'nmi_enabled' & 'ctr_running' */ get_online_cpus(); - unregister_cpu_notifier(&oprofile_cpu_nb); on_each_cpu(nmi_cpu_shutdown, NULL, 1); nmi_enabled = 0; ctr_running = 0; + __unregister_cpu_notifier(&oprofile_cpu_nb); put_online_cpus(); + + cpu_notifier_register_done(); + /* make variables visible to the nmi handler: */ smp_mb(); unregister_nmi_handler(NMI_LOCAL, "oprofile"); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists