[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Xen-devel] [PATCH v2 09/10] libxl: event: Fix possible hang with libxl_osevent_beforepoll
- To: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: George Dunlap <george.dunlap@xxxxxxxxxx>
- Date: Fri, 17 Jan 2020 13:39:19 +0000
- Authentication-results: esa5.hc3370-68.iphmx.com; dkim=none (message not signed) header.i=none; spf=None smtp.pra=george.dunlap@xxxxxxxxxx; spf=Pass smtp.mailfrom=George.Dunlap@xxxxxxxxxx; spf=None smtp.helo=postmaster@xxxxxxxxxxxxxxx
- Autocrypt: addr=george.dunlap@xxxxxxxxxx; prefer-encrypt=mutual; keydata= mQINBFPqG+MBEACwPYTQpHepyshcufo0dVmqxDo917iWPslB8lauFxVf4WZtGvQSsKStHJSj 92Qkxp4CH2DwudI8qpVbnWCXsZxodDWac9c3PordLwz5/XL41LevEoM3NWRm5TNgJ3ckPA+J K5OfSK04QtmwSHFP3G/SXDJpGs+oDJgASta2AOl9vPV+t3xG6xyfa2NMGn9wmEvvVMD44Z7R W3RhZPn/NEZ5gaJhIUMgTChGwwWDOX0YPY19vcy5fT4bTIxvoZsLOkLSGoZb/jHIzkAAznug Q7PPeZJ1kXpbW9EHHaUHiCD9C87dMyty0N3TmWfp0VvBCaw32yFtM9jUgB7UVneoZUMUKeHA fgIXhJ7I7JFmw3J0PjGLxCLHf2Q5JOD8jeEXpdxugqF7B/fWYYmyIgwKutiGZeoPhl9c/7RE Bf6f9Qv4AtQoJwtLw6+5pDXsTD5q/GwhPjt7ohF7aQZTMMHhZuS52/izKhDzIufl6uiqUBge 0lqG+/ViLKwCkxHDREuSUTtfjRc9/AoAt2V2HOfgKORSCjFC1eI0+8UMxlfdq2z1AAchinU0 eSkRpX2An3CPEjgGFmu2Je4a/R/Kd6nGU8AFaE8ta0oq5BSFDRYdcKchw4TSxetkG6iUtqOO ZFS7VAdF00eqFJNQpi6IUQryhnrOByw+zSobqlOPUO7XC5fjnwARAQABtCRHZW9yZ2UgVy4g RHVubGFwIDxkdW5sYXBnQHVtaWNoLmVkdT6JAlcEEwEKAEECGwMFCwkIBwMFFQoJCAsFFgID AQACHgECF4ACGQEWIQTXqBy2bTNXPzpOYFimNjwxBZC0bQUCXEowWQUJDCJ7dgAKCRCmNjwx BZC0beKvEACJ75YlJXd7TnNHgFyiCJkm/qPeoQ3sFGSDZuZh7SKcdt9+3V2bFEb0Mii1hQaz 3hRqZb8sYPHJrGP0ljK09k3wf8k3OuNxziLQBJyzvn7WNlE4wBEcy/Ejo9TVBdA4ph5D0YaZ nqdsPmxe/xlTFuSkgu4ep1v9dfVP1TQR0e+JIBa/Ss+cKC5intKm+8JxpOploAHuzaPu0L/X FapzsIXqgT9eIQeBEgO2hge6h9Jov3WeED/vh8kA7f8c6zQ/gs5E7VGALwsiLrhr0LZFcKcw kI3oCCrB/C/wyPZv789Ra8EXbeRSJmTjcnBwHRPjnjwQmetRDD1t+VyrkC6uujT5jmgOBzaj KCqZ8PcMAssOzdzQtKmjUQ2b3ICPs2X13xZ5M5/OVs1W3TG5gkvMh4YoHi4ilFnOk+v3/j7q 65FG6N0JLb94Ndi80HkIOQQ1XVGTyu6bUPaBg3rWK91Csp1682kD/dNVF3FKHrRLmSVtmEQR 5rK0+VGc/FmR6vd4haKGWIRuPxzg+pBR77avIZpU7C7+UXGuZ5CbHwIdY8LojJg2TuUdqaVj yxmEZLOA8rVHipCGrslRNthVbJrGN/pqtKjCClFZHIAYJQ9EGLHXLG9Pj76opfjHij3MpR3o pCGAh6KsCrfrsvjnpDwqSbngGyEVH030irSk4SwIqZ7FwLkBDQRUWmc6AQgAzpc8Ng5Opbrh iZrn69Xr3js28p+b4a+0BOvC48NfrNovZw4eFeKIzmI/t6EkJkSqBIxobWRpBkwGweENsqnd 0qigmsDw4N7J9Xx0h9ARDqiWxX4jr7u9xauI+CRJ1rBNO3VV30QdACwQ4LqhR/WA+IjdhyMH wj3EJGE61NdP/h0zfaLYAbvEg47/TPThFsm4m8Rd6bX7RkrrOgBbL/AOnYOMEivyfZZKX1vv iEemAvLfdk2lZt7Vm6X/fbKbV8tPUuZELzNedJvTTBS3/l1FVz9OUcLDeWhGEdlxqXH0sYWh E9+PXTAfz5JxKH+LMetwEM8DbuOoDIpmIGZKrZ+2fQARAQABiQNbBBgBCgAmAhsCFiEE16gc tm0zVz86TmBYpjY8MQWQtG0FAlxKMJ4FCQnQ/OQBKcBdIAQZAQoABgUCVFpnOgAKCRCyFcen x4Qb7cXrCAC0qQeEWmLa9oEAPa+5U6wvG1t/mi22gZN6uzQXH1faIOoDehr7PPESE6tuR/vI CTTnaSrd4UDPNeqOqVF07YexWD1LDcQG6PnRqC5DIX1RGE3BaSaMl2pFJP8y+chews11yP8G DBbxaIsTcHZI1iVIC9XLhoeegWi84vYc8F4ziADVfowbmbvcVw11gE8tmALCwTeBeZVteXjh 0OELHwrc1/4j4yvENjIXRO+QLIgk43kB57Upr4tP2MEcs0odgPM+Q+oETOJ00xzLgkTnLPim C1FIW2bOZdTj+Uq6ezRS2LKsNmW+PRRvNyA5ojEbA/faxmAjMZtLdSSSeFK8y4SoCRCmNjwx BZC0bevWEACRu+GyQgrdGmorUptniIeO1jQlpTiP5WpVnk9Oe8SiLoXUhXXNj6EtzyLGpYmf kEAbki+S6WAKnzZd3shL58AuMyDxtFNNjNeKJOcl6FL7JPBIIgIp3wR401Ep+/s5pl3Nw8Ii 157f0T7o8CPb54w6S1WsMkU78WzTxIs/1lLblSMcvyz1Jq64g4OqiWI85JfkzPLlloVf1rzy ebIBLrrmjhCE2tL1RONpE/KRVb+Q+PIs5+YcZ+Q1e0vXWA7NhTWFbWx3+N6WW6gaGpbFbopo FkYRpj+2TA5cX5zW148/xU5/ATEb5vdUkFLUFVy5YNUSyeBHuaf6fGmBrDc47rQjAOt1rmyD 56MUBHpLUbvA6NkPezb7T6bQpupyzGRkMUmSwHiLyQNJQhVe+9NiJJvtEE3jol0JVJoQ9WVn FAzPNCgHQyvbsIF3gYkCYKI0w8EhEoH5FHYLoKS6Jg880IY5rXzoAEfPvLXegy6mhYl+mNVN QUBD4h9XtOvcdzR559lZuC0Ksy7Xqw3BMolmKsRO3gWKhXSna3zKl4UuheyZtubVWoNWP/bn vbyiYnLwuiKDfNAinEWERC8nPKlv3PkZw5d3t46F1Dx0TMf16NmP+azsRpnMZyzpY8BL2eur feSGAOB9qjZNyzbo5nEKHldKWCKE7Ye0EPEjECS1gjKDwbkBDQRUWrq9AQgA7aJ0i1pQSmUR 6ZXZD2YEDxia2ByR0uZoTS7N0NYv1OjU8v6p017u0Fco5+Qoju/fZ97ScHhp5xGVAk5kxZBF DT4ovJd0nIeSr3bbWwfNzGx1waztfdzXt6n3MBKr7AhioB1m+vuk31redUdnhbtvN7O40MC+ fgSk5/+jRGxY3IOVPooQKzUO7M51GoOg4wl9ia3H2EzOoGhN2vpTbT8qCcL92ZZZwkBRldoA Wn7c1hEKSTuT3f1VpSmhjnX0J4uvKZ1V2R7rooKJYFBcySC0wa8aTmAtAvLgfcpe+legOtgq DKzLuN45xzEjyjCiI521t8zxNMPJY9FiCPNv0sCkDwARAQABiQI8BBgBCgAmAhsMFiEE16gc tm0zVz86TmBYpjY8MQWQtG0FAlxKNJYFCQnQrVkACgkQpjY8MQWQtG2Xxg//RrRP+PFYuNXt 9C5hec/JoY24TkGPPd2tMC9usWZVImIk7VlHlAeqHeE0lWU0LRGIvOBITbS9izw6fOVQBvCA Fni56S12fKLusWgWhgu03toT9ZGxZ9W22yfw5uThSHQ4y09wRWAIYvhJsKnPGGC2KDxFvtz5 4pYYNe8Icy4bwsxcgbaSFaRh+mYtts6wE9VzyJvyfTqbe8VrvE+3InG5rrlNn51AO6M4Wv20 iFEgYanJXfhicl0WCQrHyTLfdB5p1w+072CL8uryHQVfD0FcDe+J/wl3bmYze+aD1SlPzFoI MaSIXKejC6oh6DAT4rvU8kMAbX90T834Mvbc3jplaWorNJEwjAH/r+v877AI9Vsmptis+rni JwUissjRbcdlkKBisoUZRPmxQeUifxUpqgulZcYwbEC/a49+WvbaYUriaDLHzg9xisijHwD2 yWV8igBeg+cmwnk0mPz8tIVvwi4lICAgXob7HZiaqKnwaDXs4LiS4vdG5s/ElnE3rIc87yru 24n3ypeDZ6f5LkdqL1UNp5/0Aqbr3EiN7/ina4YVyscy9754l944kyHnnMRLVykg0v+kakj0 h0RJ5LbfLAMM8M52KIA3y14g0Fb7kHLcOUMVcgfQ3PrN6chtC+5l6ouDIlSLR3toxH8Aam7E rIFfe2Dk+lD9A9BVd2rfoHA=
- Delivery-date: Fri, 17 Jan 2020 13:39:27 +0000
- Ironport-sdr: Tr/INxwOMDbFEuv0UNKmuaofXnaClOiAc6dCLG5XmAAixjCmOfZhJqYnmCgqluWKK9H9nUJXI9 O6oDmMGj4zHDAEnW6IGcT+N7BaAl3Ay5nAZCTvsSjAfZfaav9FzqFzYta+6oF76E2hYnVUnXCZ YeVxZWEsNPV4f5cxWKBuVwdeBKTR4bZBu2NoNVyw9NXfeyu3hmm8od6S/YdXd6p95tL3MWJApj aVA3kBCuIvqHZCWFcFetRmi7Fjfa2f1Ulyww33fVRop5ZGqPadbeRHYBTbqgaPraym12LtJQf4 Puo=
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
- Openpgp: preference=signencrypt
On 1/13/20 5:08 PM, Ian Jackson wrote:
> If the application uses libxl_osevent_beforepoll, a similar hang is
> possible to the one described and fixed in
> libxl: event: Fix hang when mixing blocking and eventy calls
> Application behaviour would have to be fairly unusual, but it
> doesn't seem sensible to just leave this latent bug.
>
> We fix the latent bug by waking up the "poller_app" pipe every time we
> add osevents. If the application does not ever call beforepoll, we
> write one byte to the pipe and set pipe_nonempty and then we ignore
> it. We only write another byte if beforepoll is called again.
>
> Normally in an eventy program there would only be one thread calling
> libxl_osevent_beforepoll. The effect in such a program is to
> sometimes needlessly go round the poll loop again if a timeout
> callback becomes interested in a new osevent. We'll fix that in a
> moment.
>
> Signed-off-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
Same as the comment on patch 5:
Reviewed-by: George Dunlap <george.dunlap@xxxxxxxxxx>
_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel
|
