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kthread_stop always returning -EINTR?
by Martin Galvan July 18, 2017

July 18, 2017

Hi everyone! I'm doing a bit of testing on the Linux kthread functions, and have the following module: #include <linux/module.h> #include <linux/kthread.h> #include <linux/sched.h> #include <linux/smp.h> #include <linux/cpumask.h> #include <linux/err.h> MODULE_LICENSE("GPL"); int function(void *data) { printk(KERN_DEBUG "CPU: %u\n", smp_processor_id()); do_exit(0); /* Not sure if this is ok */ } /* Function executed upon loading driver */ int __init init_module(void) { unsigned int cpu; printk(KERN_DEBUG "init\n"); for_each_present_cpu(cpu) { struct task_struct *thread = kthread_create(function, NULL, "Thread %u", cpu); if (!IS_ERR(thread)) { int result; /* Bind the thread to the current core */ kthread_bind(thread, cpu); /* Start the thread */ wake_up_process(thread); /* Wait for the thread function to complete */ result = kthread_stop(thread); printk(KERN_DEBUG "Thread %u stopped with result %d\n", cpu, result); } else { printk(KERN_ALERT "Could not create a thread bound to core number %u\n", cpu); break; } } return 0; } /* Function executed when unloading module */ void cleanup_module(void) { printk(KERN_DEBUG "exit\n"); } >From what I understood, I should be able to see all the "CPU: ..." prints before init_module ends. However, kthread_stop is always returning -EINTR, as if wake_up_process wasn't actually being called. What am I doing wrong? (Please CC me directly when you answer this)

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new sysctl tunable knob for tcpip
by Massimo Sala July 18, 2017

July 18, 2017

I have an idea about a new sysctl knob. It is under net.ipv4. q1) which is the right kernel m-list to discuss it ? 2) any suggestion how to gain the critical mass of consensus ? 3) at first : is it mandatory to code the patch ? optional ... but better for 2) ? best regards, Sala

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[PATCH v4] staging: rtl8723bs: Place constant at the right.
by Shreeya Patel July 18, 2017

July 18, 2017

Move constant to the right of the relational operator to follow the pattern which is more common in kernel code". Problem found by checkpatch. Signed-off-by: Shreeya Patel <shreeya.patel23498(a)gmail.com> --- Changes in v4: -Make the commit message more appropriate. drivers/staging/rtl8723bs/core/rtw_btcoex.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/staging/rtl8723bs/core/rtw_btcoex.c b/drivers/staging/rtl8723bs/core/rtw_btcoex.c index 3c5cb78..01f78d1 100644 --- a/drivers/staging/rtl8723bs/core/rtw_btcoex.c +++ b/drivers/staging/rtl8723bs/core/rtw_btcoex.c @@ -55,7 +55,7 @@ void rtw_btcoex_ConnectNotify(struct adapter *padapter, u8 action) void rtw_btcoex_MediaStatusNotify(struct adapter *padapter, u8 mediaStatus) { - if ((RT_MEDIA_CONNECT == mediaStatus) + if ((mediaStatus == RT_MEDIA_CONNECT) && (check_fwstate(&padapter->mlmepriv, WIFI_AP_STATE) == true)) { rtw_hal_set_hwreg(padapter, HW_VAR_DL_RSVD_PAGE, NULL); } -- 2.7.4

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[PATCH 390/390] staging:rtl8723bs:core:rtw_btcoex: Fixed checkpatch.pl warning on 'Comparisons should place the constant on the right side of the test'.
by Shreeya Patel July 18, 2017

July 18, 2017

Fixed a coding style issue. Signed-off-by: Shreeya Patel <shreeya.patel23498(a)gmail.com> --- drivers/staging/rtl8723bs/core/rtw_btcoex.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/staging/rtl8723bs/core/rtw_btcoex.c b/drivers/staging/rtl8723bs/core/rtw_btcoex.c index 3c5cb78..01f78d1 100644 --- a/drivers/staging/rtl8723bs/core/rtw_btcoex.c +++ b/drivers/staging/rtl8723bs/core/rtw_btcoex.c @@ -55,7 +55,7 @@ void rtw_btcoex_ConnectNotify(struct adapter *padapter, u8 action) void rtw_btcoex_MediaStatusNotify(struct adapter *padapter, u8 mediaStatus) { - if ((RT_MEDIA_CONNECT == mediaStatus) + if ((mediaStatus == RT_MEDIA_CONNECT) && (check_fwstate(&padapter->mlmepriv, WIFI_AP_STATE) == true)) { rtw_hal_set_hwreg(padapter, HW_VAR_DL_RSVD_PAGE, NULL); } -- 2.7.4

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why inode reference i_count = 1 for all executable and libraries ?
by Lev Olshvang July 12, 2017

July 12, 2017

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Camera Driver
by Wasim Akram July 12, 2017

July 12, 2017

What is the difference between iso buffer and sio buffer in camera driver code ?

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Query regarding kernel modules intercepting system call.
by Ajinkya Surnis July 9, 2017

July 9, 2017

Hi guys, I'm new to kernelnewbies and this is my first question in the list. I'm working on system call interception (for open() system call) and I got one problem: I have two kernel modules (mod1 and mod2) and both of them are trying to intercept open() syscall. I've loaded mod1 first and then mod2. The mod1 intercepted open() by: original_open1 = sys_call_table[__NR_open]; sys_call_table[__NR_open] = mod1_open; Here original_open1 would be sys_open. After this, mod2 intercepted open() by: original_open2 = sys_call_table[__NR_open]; sys_call_table[__NR_open] = mod2_open; Here, original_open2 would be mod1_open() since mod1 was loaded first. Now, the problem is: Suppose I unload mod1 first and open() system call gets executed, then mod2_open() would get called, which ultimately calls mod1_open(). Since mod1 is already unloaded, calling mod1_open() caused panic (since the function pointer is no longer a valid memory region). I need some mechanism to avoid this problem. Basically, I want a solution which facilitates loading/unloading the modules (which intercept same syscall) in any random order without causing any panic. Is there some kind of facility such that while unloading the module (`mod2` here), the module will broadcast the message to all other modules that it's being unloaded and instead of refering to `original_open2()` the other modules should use `original_open1()`. Your help would really be appreciated. Thanks, Ajinkya.

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is `mixing declarations and code' allowed?
by Shiyao Ma July 8, 2017

July 8, 2017

Hi, One thing I feel very un-comfortable when writing kernel module code is the warning of `mixing declarations and code'. Is `mixing declarations and code' still frowned upon by kernel developers? Or is it just a history burden that for some reason one can not mix `declarations and code'? Best,

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how to get consistent value of "nf_conntrack_htable_size" and "nf_conntrack_hash" in a kernel module ?
by Shiyao Ma July 7, 2017

July 7, 2017

Hi, I want to foreach all the `struct nf_conn's in my out-of-tree kernel module. My plan is to get the `nf_conntrack_htable_size' and `nf_conntrack_hash', then do some read on the hash table. However, the symbol `nf_conntrack_generation' is not exported, so I cannot do things like this: struct hlist_nulls_head *hptr; unsigned int sequence, hsz; do { sequence = read_seqcount_begin(&nf_conntrack_generation); hsz = nf_conntrack_htable_size; hptr = nf_conntrack_hash; } while (read_seqcount_retry(&nf_conntrack_generation, sequence)); How to get a consistent value of `nf_conntrack_htable_size' and `nf_conntrack_hash' ? Thanks.

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Can I use the same .config file to compile 32-bit and 64-bit kernel?
by Hao Lee July 7, 2017

July 7, 2017

Hi, I'm currently configuring a custom kernel on Fedora x86_64. The first option on the configuration menu is "64-bit kernel" which I think is the only option controlling the architecture of kernel. Copying this .config file to a 32-bit system directly and turning off this option, can I compile a 32-bit kernel which doesn't have any hidden problems? If this way is feasible, I think the only difference between these two kernels is architecture. Regards, Hao Lee

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