Messages in this thread | | | Date | Sat, 4 Sep 1999 18:55:03 +0530 (IST) | From | Sushil Agrawal <> | Subject | Re: SMP linux help |
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Hi, Thanks Matthew for the help. Does that mean that as of now (in linux 2.2.9) the spin_lock(&lastpid_lock) and read_lock(&tasklist_lock) in the get_pid() function in fork.c are redundant?
Also, why is current->lock_depth used in lock_kernel() macro? We could have just used kernel_flag as a lock variable?
Bye, Sushil.
On Sat, 4 Sep 1999, Matthew Wilcox wrote:
> > The lock_kernel locks the entire kernel; this is sometimes referred > to as the big kernel lock. Originally, this was the only lock, and > was acquired whenever the kernel was entered. The big lock is being > replaced in certain places by finer-grained locking and mutexes, but > this task is not yet complete. > > On Sat, Sep 04, 1999 at 05:55:38PM +0530, sushil@iitk.ac.in wrote: > > Hi, > > I am running linux 2.9.9 kernel. > > I am trying the understand the locking mechanism used in linux to make > > the kernel SMP safe. In do_fork() (also in many other syscall interface > > functions) there is call to lock_kernel() function. What does > > lock_kernel() do? If it is used to synchronize the access to kernel data > > structures from other processes on other processors, then why, after > > having called this function, we again try to do some locking like calling > > spin_lock(&lastpid_lock) in get_pid()? > > > > I have seen the definition of lock_kernel. It increments the > > current->lock_depth and if it nonzero then tries to lock the kernel_flag > > variable. > > > > Kindly reply. > > I am on this mailing list. > > > > Thanks, > > Sushil. > > > > > > > > > > > > - > > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > > the body of a message to majordomo@vger.rutgers.edu > > Please read the FAQ at http://www.tux.org/lkml/ > > -- > Matthew Wilcox <willy@bofh.ai> > "Windows and MacOS are products, contrived by engineers in the service of > specific companies. Unix, by contrast, is not so much a product as it is a > painstakingly compiled oral history of the hacker subculture." - N Stephenson > > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.rutgers.edu > Please read the FAQ at http://www.tux.org/lkml/ > >
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.rutgers.edu Please read the FAQ at http://www.tux.org/lkml/
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