Date: Fri, 10 Mar 2017 14:24:52 +0100 From: Alexandre Martins <alexandre.martins@stormshield.eu> To: Konstantin Belousov <kostikbel@gmail.com> Cc: freebsd-current <freebsd-current@freebsd.org> Subject: Re: smp_rendezvous_action: Are atomics correctly used ? Message-ID: <1584060.AQ0HNTQbMq@pc-alex> In-Reply-To: <20170309142516.GA16105@kib.kiev.ua> References: <2092905.6A8RAGlt18@pc-alex> <3034263.GEZH9i4V44@pc-alex> <20170309142516.GA16105@kib.kiev.ua>
next in thread | previous in thread | raw e-mail | index | archive | help
--nextPart2805968.SMjhqhfdD7 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="iso-8859-1" Le jeudi 9 mars 2017, 16:25:17 Konstantin Belousov a =E9crit : > On Thu, Mar 09, 2017 at 02:52:09PM +0100, Alexandre Martins wrote: > > Le jeudi 9 mars 2017, 15:07:54 Konstantin Belousov a ?crit : > > > On Thu, Mar 09, 2017 at 10:59:27AM +0100, Alexandre Martins wrote= : > > > > I have the save question for the cpu_ipi_pending here: > > > >=20 > > > > https://svnweb.freebsd.org/base/head/sys/x86/x86/mp_x86.c?view=3D= annotat > > > > e#l1 > > > > 080> > > > >=20 > > > > Le jeudi 9 mars 2017, 10:43:14 Alexandre Martins a ?crit : > > > > > Hello, > > > > >=20 > > > > > I'm curently reading the code of the function smp_rendezvous_= action, > > > > > in > > > > > kern/subr_smp.c file. In that function, i see that the variab= le > > > > > smp_rv_waiters is read in some while() loop in a non-atomic w= ay. > > > > >=20 > > > > > https://svnweb.freebsd.org/base/head/sys/kern/subr_smp.c?view= =3Dannota > > > > > te#l > > > > > 412 > > > > > https://svnweb.freebsd.org/base/head/sys/kern/subr_smp.c?view= =3Dannota > > > > > te#l > > > > > 458 > > > > > https://svnweb.freebsd.org/base/head/sys/kern/subr_smp.c?view= =3Dannota > > > > > te#l > > > > > 472 > > > > >=20 > > > > > I suspect one of my freeze to be due by that. > > >=20 > > > You should provide either evidence or, at least, some reasoning > > > supporting > > > your claims. > >=20 > > I curently have a software watchdog that triger and does a coredump= . In > > the > > coredumps, I always see a CPU trying to write-lock a "rm lock". Eve= ry > > time, > > that CPU is spinning into the smp_rendezvous_action, in the first w= hile > > loop) while the others are into the idle threads. > >=20 > > The fact is that freeze is not clear and I start to search "exotic"= causes > > to explain it. >=20 > This sounds as the 'usual' deadlock, where some other thread owns rml= ock in > read mode. I recommend you to follow the > https://www.freebsd.org/doc/en_US.ISO8859-1/books/developers-handbook= /kernel > debug-deadlocks.html Just a last question, for my personnal knowledge. In ARM >=3D 6, for atomic acces, the code should (?) use LDREX and STRE= X for, I=20 quote : "Use LDREX and STREX to implement interprocess communication in= =20 multiple-processor and shared-memory systems." (see here :=20 http://infocenter.arm.com/help/index.jsp?topic=3D/com.arm.doc.dui0489e/= Cihbghef.html But, in that while loop, it's a standard "LDR" that is used. Is it corr= ect=20 too, and why ? =2D-=20 Alexandre Martins STORMSHIELD --nextPart2805968.SMjhqhfdD7 Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExDzANBglghkgBZQMEAgEFADCABgkqhkiG9w0BBwEAAKCCCOUw ggSGMIICbqADAgECAgUA28zw7TANBgkqhkiG9w0BAQsFADBIMQswCQYDVQQGEwJGUjEUMBIGA1UE CgwLU1RPUk1TSElFTEQxIzAhBgNVBAMMGlN0b3Jtc2hpZWxkIFJvb3QgQXV0aG9yaXR5MB4XDTE0 MDkwNDE1MDcxMFoXDTI0MDkwMTE1MDcxMFowSTELMAkGA1UEBhMCRlIxFDASBgNVBAoMC1NUT1JN U0hJRUxEMSQwIgYDVQQDDBtTdG9ybXNoaWVsZCBVc2VycyBBdXRob3JpdHkwggEiMA0GCSqGSIb3 DQEBAQUAA4IBDwAwggEKAoIBAQDChwWgC/6VWKL7jgWI3eA2sVvRdOwuHcXsRAAXVWdlMC0ygg7u 45E78GhAnpdl8QbIu7x/Q2zOq6KttspwDEIjkoMLTZngLLlGjYJZPfuSoC6hl9R7vRd5f8Fhu3v0 xQ/7vzKYz4C836IGCrk31gmrPO0H0fxkyxCMfhoTTzue3oXW1IsmQwCrOPOu2Y82QANDhbifWLjI WJetnj58YRKR82KBs3Flbqxtp0mi9+IswMvCCRSoT+ORB73Cl6URt7Qm7BcD+qnkJ9uwlUC94dIl T2hX4ybY/w/ssA17Ew418fgyRCWQXzgjZgZ/XUcw2WP9dIggA7Pg+c/xeROJH1zvAgMBAAGjdjB0 MB0GA1UdDgQWBBShbYRsooCFBXx8dXWANMETW5fXgTAfBgNVHSMEGDAWgBS4Qqn6Z0Twf9NhjOyl x1CutL3sozAPBgNVHRMBAf8EBTADAQH/MA4GA1UdDwEB/wQEAwIBBjARBglghkgBhvhCAQEEBAMC AQYwDQYJKoZIhvcNAQELBQADggIBAE6C9zkt2J6dPm2KLbzRS6rBIYZNFi0X59g3ekQ2Sc4UWsq+ B3L86j5xnQSRnIM/DKV1+Q2UHbU/qsh4cto2fwTV6V+aJ07Vu/bJE1rAN4AI4V26ytf7VoBcBjVZ Jq8pHOMp/G2eQH7F1xqzml68DpKku66aUalkcC9IM82m7AW3YAyvDoYEAchv4qyL8qhVLLp6LNru 8ZOhMELhZLWl4ulw/SFDMhcBS6I4wC6icj71MLGSrr61vMktMdwQ+CGFQ5z5JbaxM61VgzKay8+g lw+xTbpnitrDfhkzHs2fdwOOur3vtNnNsrdBWiYPseJ2k4VGD7ov5kITQZckmZyF/V+Ir//agJQG VuwhDZCXgXOvrje+FLYp7tQ9pgSvLbluh1A+ywfyHnFI4n6tZy9SD3MIDgWR4KwFLM1Qmt3NQb32 tkq9Vm0jUcQXFfbnWKLA9krw3m8NmCqhL5PzpfOegYOc0QJWfMQamxeWxXMLk6uKisS//+VqfpCa 5Jx53t+9DmoN1+ob4jOprPaX6tfBBr5djah2yzPGjHEB52VgWXxIF9lCM2z7Qw+zFb2PIdNeSjIk NEFg/1orKAAa5gQXAQynN2J7E+aLf2XLhHcS0v+9yoisPEw9+Tb5F1uQh+gzYD5JUUYcYWncnX8g P8k6X+F5mQ/81IoNL/IejxJgy/LoMIIEVzCCAz+gAwIBAgIFAIUoy7swDQYJKoZIhvcNAQELBQAw STELMAkGA1UEBhMCRlIxFDASBgNVBAoMC1NUT1JNU0hJRUxEMSQwIgYDVQQDDBtTdG9ybXNoaWVs ZCBVc2VycyBBdXRob3JpdHkwHhcNMTYwOTAxMTUxMTA4WhcNMTcwOTAxMTUxMTA4WjBwMQswCQYD VQQGEwJGUjEUMBIGA1UECgwLU1RPUk1TSElFTEQxGjAYBgNVBAMMEUFsZXhhbmRyZSBNQVJUSU5T MS8wLQYJKoZIhvcNAQkBFiBhbGV4YW5kcmUubWFydGluc0BzdG9ybXNoaWVsZC5ldTCCASIwDQYJ KoZIhvcNAQEBBQADggEPADCCAQoCggEBAMN+CnvE13jKEwJ+OyMzwBpC02dY+LpD5luJwnJTVnV2 9aUjEMI+xGFMMHd9kSIVInbk4WDe1ELOKerg0dzgnkRiOHECSGum1UhcZABxQgY2cmSffNQ6JVro 52UaBlt3aTOk3imYJCHUIGgOWMvOtRc8BxyBHdi15FZPj/F9I+AKufRFsBXUakplFIAPEwy3m2eR a/eCMLqGJUyK7YmsAlEnYn2mA38zIoqtKvL6KPHtrV8fw1SRLQ13+j9nu1LlCaqhmLtILFxhV0/9 uDTvx5cKtZ8Xj1nPM6NUUrso9qlXwm4On6Y34pVTtnYGMQRuljil3Hiz84RJjPDJYRGwbgkCAwEA AaOCAR0wggEZMB0GA1UdDgQWBBTmRLIwSfhNwbdfV13xt0G0JHYjPDAfBgNVHSMEGDAWgBShbYRs ooCFBXx8dXWANMETW5fXgTAJBgNVHRMEAjAAMA4GA1UdDwEB/wQEAwID6DARBglghkgBhvhCAQEE BAMCBLAwHQYDVR0lBBYwFAYIKwYBBQUHAwQGCCsGAQUFBwMCMEoGA1UdHwRDMEEwP6A9oDuGOWh0 dHBzOi8vcGtpLm5ldGFzcS5jb20vYXV0aC9jZXJ0aWZpY2F0ZXJldm9jYXRpb25saXN0LmNybDAR BgNVHSAECjAIMAYGBFUdIAAwKwYDVR0RBCQwIoEgYWxleGFuZHJlLm1hcnRpbnNAc3Rvcm1zaGll bGQuZXUwDQYJKoZIhvcNAQELBQADggEBALT9NWiAaE6nDev34vShhsyb9lWBOQfCnAMyKwtFy/cU uIoHsxyOanIIQHz0ZtB76GCHDo7RStMyp6RYIefIsxABLhSr4hHapJka9g/X/nxexyr0xyT3IpYQ dmyMSHRT18Z/ZaBlQdyfnS2PYkPHJAHl4iqB4SnQlh3rwFdKTJMgCz413cDxQHytgRPGTiXOhyV7 aS3ANJFha6ZHA8HU9sTslY8ZXSUu94iD3t2kcF3gBb432UKALwryKqnrwzFX68pFpqO5QAjEHaF6 6p1agMb2b3HlQGZrME5wSO6rsZJPYvJEyvrwHxCxjSTkOdPw6GriWGTMrVMU0fVrfptMS1gxggIT MIICDwIBATBSMEkxCzAJBgNVBAYTAkZSMRQwEgYDVQQKDAtTVE9STVNISUVMRDEkMCIGA1UEAwwb U3Rvcm1zaGllbGQgVXNlcnMgQXV0aG9yaXR5AgUAhSjLuzANBglghkgBZQMEAgEFAKCBkzAYBgkq hkiG9w0BCQMxCwYJKoZIhvcNAQcBMBwGCSqGSIb3DQEJBTEPFw0xNzAzMTAxMzI0NTJaMCgGCSqG SIb3DQEJDzEbMBkwCwYJYIZIAWUDBAECMAoGCCqGSIb3DQMHMC8GCSqGSIb3DQEJBDEiBCAoctU2 d1qaGvBg31MZQOB+NJojk3ycQ8NvmWZpzfCkgzANBgkqhkiG9w0BAQEFAASCAQC7/eVgoNBuUw44 7Ho03IwnxHPBMiFKHlibaZwfo2eEFKB6tthtzJbnTZQvig5HHBf+3lfos3jlJWGg5M+esgpjfWGJ IOu4z7571vZgewZzwLIwn7frjBkl4wv5F4/kQNWHfMZwffkVvPSu2rOeXd4n1QdnUNvbNn9IbDRa G/CCt9h3ZpibR6Fi3aQD6zYurmY2xvjck/U7sQAZRLzBSbcfhhhy1KqIUC3OgGhLSGyaNQ3yNQj7 FE7IzgX6MAr0lTuUpf3cS7++AOvrjxA/gwC3MMhDKOILBhwnlSE5k42dmypptUNvJH0lfZDrNUC5 Gr24IlFbumkQ/aX2g81m5v8QAAAAAAAA --nextPart2805968.SMjhqhfdD7--
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?1584060.AQ0HNTQbMq>