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Old 09-07-2012, 01:02 AM   #1
sanrio alvares
LQ Newbie
Registered: Apr 2010
Location: Mumbai, India
Distribution: ubuntu, fedora, android
Posts: 12

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Who wakes the kthreadd daemon during SD card read?

I would like to know who wakes the kthread daemon up, when a read from the SD card is done using vfs_read. According to the code flow the kthreadd will wake up the mmcqd (mmc_queue_thread) which will process the read/write requests to the SD driver.

The issue I am facing here is although the vfs_read to the SD card is called by the USB Mass Storage driver, the read does not proceed to the mmc_queue_thread. This leads to old contents of the SD card being shown on PC.

Here is the kernel stack after vfs_read generated from sdhci_send_command(). ------------[ cut here ]------------ WARNING: at /vobs/iandroid/src/kernel/drivers/mmc/host/mx_sdhci.c:495 sdhci_send_command+0x120/0x758() Modules linked in: g_mot_android mxc91341_oh_udc sipcttydrv aplogger coredump bploader sipcdrv mu_drv [] (dump_stack+0x0/0x14) from [] (warn_slowpath+0x68/0x84)

[] (warn_slowpath+0x0/0x84) from [] (sdhci_send_command+0x120/0x758) r3:00000033 r2:00000000 r7:c6605f04 r6:c6605f5c r5:c65305c0 r4:c0409510

[] (sdhci_send_command+0x0/0x758) from [] (sdhci_request+0x188/0x1bc)

[] (sdhci_request+0x0/0x1bc) from [] (mmc_wait_for_req+0x110/0x128) r8:c656f870 r7:c6605dc8 r6:00000000 r5:c6530400 r4:c6605ef0

[] (mmc_wait_for_req+0x0/0x128) from [] (mmc_blk_issue_rq+0x1f4/0x7b0) r7:c642ae00 r6:00000000 r5:c64daeac r4:c64daea0

[] (mmc_blk_issue_rq+0x0/0x7b0) from [] (mmc_queue_thread+0x134/0x154)

[] (mmc_queue_thread+0x0/0x154) from [] (kthread+0x54/0x80) r8:00000000 r7:00000000 r6:00000000 r5:c0248330 r4:fffffffc

[] (kthread+0x0/0x80) from [] (do_exit+0x0/0x738) r5:00000000 r4:00000000 ---[ end trace 24b57c573e7a44e3 ]---


devicedrivers, filesystems, kernel, mmc

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